Continued attendance in a PrEP program despite low adherence and non-protective drug levels among adolescent girls and young women in Kenya: Results from a prospective cohort study.

BACKGROUND: In sub-Saharan Africa (SSA), adolescent girls and young women (AGYW) ages 15 to 24 years represent <10% of the population yet account for 1 in 5 new HIV infections. Although oral pre-exposure prophylaxis (PrEP) with tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) can be highly effective, low persistence in PrEP programs and poor adherence have limited its ability to reduce HIV incidence among women. METHODS AND
FINDINGS: A total of 336 AGYW participating in the PEPFAR-funded DREAMS PrEP program in western Kenya were enrolled into a study of PrEP use conducted between 6/2019 to 1/2020. AGYW, who used daily oral TDF/FTC, completed interviews and provided dried blood spots (DBS) for measurement of tenofovir-diphosphate (TFV-DP) concentrations at enrollment and 3 months later, and 176/302 (58.3%, 95% confidence interval [95% CI 52.3 to 63.8]) met our definition of PrEP persistence: having expressed intention to use PrEP and attended both the second interview and an interim refill visit. Among AGYW with DBS taken at the second interview, only 9/197 (4.6%, [95% CI 1.6 to 7.5]) had protective TFV-DP levels (≥700 fmol/punch) and 163/197 (82.7%, [95% CI 77.5 to 88]) had levels consistent with no recent PrEP use (<10 fmol/punch). Perception of being at moderate-to-high risk for HIV if not taking PrEP was associated with persistence (adjusted odds ratio, 10.17 [95% CI 5.14 to 20.13], p < 0.001) in a model accounting for county of residence and variables that had p-value <0.1 in unadjusted analysis (age, being in school, initiated PrEP 2 to 3 months before the first interview, still active in DREAMS, having children, having multiple sex partners, partner aware of PrEP use, partner very supportive of PrEP use, partner has other partners, AGYW believes that a partner puts her at risk, male condom use, injectable contraceptive use, and implant contraceptive use). Among AGYW who reported continuing PrEP, >90% indicated they were using PrEP to prevent HIV, although almost all had non-protective TFV-DP levels. Limitations included short study duration and inclusion of only DREAMS participants.
CONCLUSIONS: Many AGYW persisted in the PrEP program without taking PrEP frequently enough to receive benefit. Notably, AGYW who persisted had a higher self-perceived risk of HIV infection. These AGYW may be optimal candidates for long-acting PrEP.

Introduction

While remarkable progress has been made in reducing overall HIV incidence, young women still bear a disproportionate burden of new infections [1,2]. In sub-Saharan Africa (SSA), adolescent girls and young women (AGYW) represent less than 10% of the population yet account for 1 in 5 new HIV infections [1]. Oral pre-exposure prophylaxis (PrEP) with tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) has proved to be a highly effective HIV prevention intervention. Clinical trials and program settings have demonstrated roughly 95% efficacy in men who have sex with men (MSM) who adhere to daily or on-demand dosing [3-7]. In contrast, daily oral PrEP for HIV prevention among women has been less successful, in large part due to low adherence [8-10]. Obstacles including lack of partner support, need to conceal PrEP use from partners, lack of privacy from family members, and low empowerment hinder effective daily oral PrEP use in women, particularly in SSA [11,12].

Injectable long-acting cabotegravir (CAB-LA) provided high-level protection in clinical trials in both MSM and transgender women in the Americas, Asia, and Africa [13] and women in SSA [14] and was found to offer superior HIV prevention relative to oral daily TDF/FTC. In the study in SSA, analysis of dried blood spot (DBS) samples from women in the oral TDF/FTC arm, throughout 1.2 years median follow-up in this trial, showed undetectable levels in 38%, and only 18% with concentrations consistent with 4+ doses/week. That is, women were persistent in visit attendance but not adherent to daily pill use. In contrast, injection coverage was 93% of person-years.

These results expand the possibilities for more effective PrEP use among women. Importantly, many women in clinical trials of daily oral PrEP in SSA continued to attend study visits but did not adhere to daily dosing. Thus, this new modality provides an avenue for more successful HIV prevention, much as implants and injectable contraception offer greater success for pregnancy prevention among women in SSA [15]. A critical next step will be bridging the CAB-LA clinical trial results to real-world settings, especially since prior studies suggest that PrEP visit continuation among AGYW is much higher in clinical trials than in programmatic settings (public and private clinics) [16].

Understanding women who are persistent but not adherent and providing them with long-acting formulations may be a more effective way to reduce population-level HIV incidence. Data from programmatic settings are important for developing effective implementation strategies for these women but such data very rarely include both program persistence, which focuses on ongoing visit attendance [17-19] and objectively measured adherence. To address this, we leveraged data from the PEPFAR-funded DREAMS initiative which offers daily oral PrEP to AGYW within a program that supports HIV prevention activities. Nesting a study in this context allowed collection of data on PrEP persistence as well as self-reported and objectively measured adherence in a program setting.

Our analysis focuses on Kisumu and Homa Bay Counties of western Kenya, where PATH implements the DREAMS Initiative. About 10,500 new HIV infections were reported in young people ages 15 to 24 years in these 2 counties in 2015, accounting for 14% of the national HIV incidence [20]. As part of the DREAMS implementation, an extensive monitoring and evaluation system (DREAMS database) collects comprehensive data on each AGYW and her participation in the DREAMS program, including data on PrEP initiation and refill visits.

By November 2017, an estimated 1,060 AGYW in Kisumu and Homa Bay Counties had enrolled in the DREAMS PrEP program. The current analysis examines the PrEP use cascade as well as predictors of PrEP persistence and adherence (by self-report and drug levels) in a subset of these AGYW enrolled in a prospective study. The main questions examined were the extent of program persistence (a measure focusing on visit attendance) and the level of protection from HIV infection among program attendees as assessed by measuring PrEP metabolites in blood.

Methods

Study design, participant eligibility, and sample size

A prospective study was conducted from 6/2019 to 1/2020 among AGYW participants in the DREAMS PrEP program, which had the following eligibility criteria (1 or more): (1) a sero-discordant relationship (HIV+ partner); (2) a sexual partner of unknown HIV status; (3) transactional sex; (4) a recently diagnosed STI; (5) recurrent use of PEP; (6) sexual activity while taking alcohol or drugs; or (7) injection drug use. This study included face-to-face interviews at enrollment and 3 months later, and DBS sample collection for assays of intracellular drug metabolites (tenofovir diphosphate, TFV-DP, as an objective measure of PrEP adherence) from AGYW who reported PrEP use at the time of interview. Interviews captured self-reported adherence and factors associated with adherence and persistence among AGYW. These data were combined with PrEP program data, including refill data from the DREAMS database.

From the DREAMS database, we identified 613 AGYW who met our eligibility criteria of self-reported age between 18 to 24 years, residing in Kisumu and Homa Bay Counties, enrolled in the PrEP program for 2 to 9 months with a visit for PrEP initiation or refill between October 2018 and April 2019, and had returned for a refill in the 2 months prior to study start in June 2019 (to exclude AGYW who might have recently stopped using PrEP).

From the 613 eligible AGYW, we randomly sampled (using the “sample” command in STATA) to select and enroll 359 AGYW who met the above eligibility criteria; were able to speak English, Dholuo, or Kiswahili; and had indicated on the DREAMS enrollment consent form willingness to be contacted for future studies. This sample size assumed a discontinuation or loss to follow-up rate of 50% and a 2-level factor potentially associated with PrEP adherence. Our sample size was sufficient to detect a minimum absolute difference of 15% in PrEP adherence rates against a binary co-factor (e.g., in PrEP support group versus not in PrEP support group) at 80% power given a type I error rate of 5% and a 2-sided test.

This analysis focuses on 2 study objectives: measurement of PrEP adherence by self-report and biomarkers, and identification of factors associated with PrEP persistence and adherence. Because of very low levels of adherence, we were unable to identify associations with that outcome, as anticipated in the prospective protocol (S1 Protocol) of the study, and concentrated primarily on factors associated with persistence. The final analysis included adjustment for clustering at the ward level (a small administrative unit), which was not included in the original protocol.

Participants provided written informed consent to participate. The study was approved by the Institutional Review Board (IRB) at the Kenya Medical Research Institute (KEMRI), Fred Hutchinson Cancer Research Center, and PATH Research Ethics Committee.

Study procedures and variables

Research assistants received training in informed consent and research ethics, study procedures, interviewing techniques, and DBS sample collection and storage. We conducted one-on-one in-person structured interviews with all participants in their preferred language, entering data electronically via Open Data Kit (ODK). The instrument captured information on: (1) sociodemographic characteristics; (2) participation in and perceptions of the DREAMS program; (3) experience with PrEP and support for PrEP use among partners, family members, and the community; (4) self-reported continued use of and adherence to PrEP; (5) HIV risk perception; (6) condom and contraceptive use; (7) alcohol use (alcohol use disorder identification test (AUDIT) [21]); (8) intimate partner violence (HITS, 4 items [22,23]); (9) social support (MOS Social Support Scale, 19 items [24-27]); (10) depression (PHQ-9, 10 items [28-30]) and used scales previously employed in Kenya or other African countries [21,23,25-27,29].

A research assistant collected a DBS sample for measurement of intracellular TFV-DP levels from participants who reported they were currently taking PrEP. DBS were collected on Whatman Protein Saver 903 cards and stored in a CDC lab in Kisumu County at −70°C until shipment for testing at Chiang Mai University, Thailand.

At the follow-up visit (Interview 2) 3 to 4 months post-enrollment (Interview 1), we collected a second DBS sample from those who reported they were continuing PrEP. In all but a few cases, the research assistant who conducted the first interview also conducted the follow-up interview. TFV-DP was analyzed using validated liquid chromatography mass spectrometry (LC-MS/MS) with calibration curve range of 200 to 10,000 fmol/3mm punch. Internal/external quality control samples were included in each run, with external samples cross-validated with intra-laboratory testing. In addition to the study data collected at the 2 interviews, pharmacy PrEP refill information was obtained from the DREAMS program data.

The main outcome of interest in this study is PrEP persistence. Persistent AGYW were defined as having attended both interviews as well as at least 1 interim PrEP refill visit and stating that they were taking PrEP at both interviews. A secondary outcome is PrEP adherence based on the TFV-DP levels from the testing of the DBS samples. Adherent AGYW were defined as having TFV-DP levels of 700+ fmol/punch, the equivalent of 4+ doses per week taken regularly [31]. We included cutoffs at 350 fmol/punch, (approximately 1 to 2 days per week) [31], as well as the lower limit of quantification (200 fmol/punch) and the lower limit of detection (10 fmol/punch); levels below 10 were taken as consistent with no PrEP use in the recent past [32].

Statistical analysis

We summarized categorical variables as frequency and percentage, and continuous variables as mean and standard deviation (SD) or median and interquartile range (IQR). We used univariable and multivariable (adjusted) generalized estimating equations modification of logistic regression models accounting for clustering of AGYW within wards to assess the associations between persistence and factors measured at Interview 2. The multivariable models adjusted for county of residence and factors that had a p-value <0.1 in the univariable analysis. AGYW who were lost to follow-up or censored due to study closure prior to Interview 2 were excluded from the analysis. We focused the analysis on factors associated with persistence at Interview 2; some factors potentially influencing PrEP adherence and PrEP persistence were measured at Interview 2 only. The proportion of AGYW who attended Interview 2 and had missing information on factors of interest was <10%. The analyses were based on complete case data assuming missing completely at random for the missing data mechanism. A p-value ≤0.05 was considered statistically significant for a 2-sided test. All analyses were performed using SAS Version 9.4 (SAS Institute, Cary, North Carolina, United States of America) and graphs were plotted using R version 4.1.0. This study is reported per the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guideline (S1 STROBE Checklist).

Role of funding source

The funders were not involved in the study design or execution, data collection, data analysis, data interpretation, or writing of the manuscript.

Ethics committee approval

Ethical approvals for the study were obtained from the Institutional Review Board (IRB) at the Kenya Medical Research Institute, PATH, and Fred Hutchinson Cancer Research Center. Written informed consents were obtained for all the DREAMS participants enrolled in the study.

Results

This study recruited 359 AGYW who were enrolled in the DREAMS PrEP program. Of the 359 AGYW, 336 reported currently taking PrEP and provided a DBS at Interview 1; these 336 are the focus of this analysis. Their mean age recorded in DREAMS program data was 22 years; roughly half (45%) resided in Kisumu County, the remainder in Homa Bay County. At Interview 1, AGYW had been in the DREAMS program for 2.5 years on average and in the PrEP program for a median of 112 (IQR: 90,172) days; the majority (176/336, 52.4%) had initiated PrEP use 4 to 6 months earlier, and 42% were living with their partner, 16% reported multiple sexual partners, 37% believed their partner had other partners, 49% believed their partner’s behavior put them at risk, 73% reported inconsistent or no condom use, and 29% reported that their partner’s status was HIV+ or unknown (Table 1).

Table 1

Characteristics of 336 study participants at the first interview.

Characteristic	N	Col %
County of residence, Kisumu	152	45.2
County of residence, Homa Bay	184	54.8
Education
Primary	110	32.7
Secondary	186	55.4
Postsecondary	40	11.9
Currently in school	122	36.3
In PrEP support group	263	78.3
Currently have a sexual partner	334	99.4
1 partner	281	83.6
>1 partner	53	15.8
Married/cohabiting	144	42.9
One or more children	235	69.9
Live with parents or grandparents	162	48.2
Live with partner	141	42.0
Partner has other partners	125	37.2
AGYW believes partner puts her at risk	163	48.5
Contraceptive use	277	82.4
Oral contraceptive	13	3.9
Injectable	60	17.9
Implant	100	29.8
Male condoms	97	28.9
Female condoms	3	0.9
Other	4	1.2
Condom, consistent use	90	26.8
Condom, inconsistent/no use	246	73.2
Partner is aware of PrEP use	198	58.9
Partner is very supportive of PrEP use	131	39.0
Partner is very supportive of PrEP use among those with partner being aware	131	66.2
Partner has an unknown HIV status	83	24.7
Partner is HIV positive	14	4.2
Partner’s HIV status is positive/unknown	97	28.9
Experience of intimate partner violence (HITS IPV scale, IPV score >10)*	56	16.7
Harmful or hazardous drinking (AUDIT score ≥8)**	10	3
Depression (PHQ-9)
No depressive symptoms	116	34.5
Mild depression	142	42.3
Moderate or major depression	78	23.2
Social support (most or all the time, overall social support score > 75%)***	40	11.9
Months since PrEP initiation at interview 1, 2–3 months	87	25.9
Months since PrEP initiation at Interview 1, 4–6 months	176	52.4
Months since PrEP initiation at Interview 1, 6+ months	67	19.9

*Scores of 10 or greater on the 4-question HITS scale (“How often does your partner: physically hurt you, insult you or talk down to you, threaten you with harm, and scream or curse at you?”) are consistent with domestic violence [22].

**AUDIT was used to measure potential alcohol abuse. A score of 8 or more is associated with harmful or hazardous drinking, a score of 13 or more in women, and 15 or more in men, is likely to indicate alcohol dependence.

***Social support was measured with the MOS Social Support Survey [24] measuring receipt of support using a Likert scale where 1, 2, 3, 4, and 5 are none, a little, some, most, and all the time, respectively. Items in the 4 subscales (emotional/informational support, tangible support, affectionate support, positive social interaction) were combined by calculating the average of (1) the scores for all 18 items included in the 4 subscales, and (2) the score for the one additional item. Scale scores were transformed to a 0–100 scale using the following formula

.

A score of 75% or greater corresponds to having overall social support (averaging across all questions) most or all the time (average score of 4 or higher).

AGYW, adolescent girls and young women; AUDIT: alcohol use disorder identification test; IPV, interpersonal violence; MOS, Medical Outcomes Study; PrEP, pre-exposure prophylaxis.

.

Of the 336 AGYW taking PrEP at enrollment, 302 attended Interview 2, with 18 lost to follow-up and 16 censored. At Interview 2, 105 said they had discontinued PrEP and 197 said they were continuing PrEP (Fig 1).

Fig 1

Study flow chart showing study design and the attrition of participants at each step of the analysis.

Most (246/302, 81%) AGYW interviewed at follow-up had attended at least 1 PrEP dispensation visit between the 2 interviews. Fifty-six had no record of attendance at interim PrEP refill visits, including 21 of the 197 AGYW who reported they were continuing PrEP. This left 176 of the AGYW who attended Interview 2 who met our definition of PrEP persistence (176/302, 58.3%, [95% CI 52.7–63.8] (Figs 1 and 2A and Table A in S1 Table). AGYW, adolescent girls and young women; CI, confidence interval; DBS, dried blood spot; PrEP, pre-exposure prophylaxis.

Fig 2

PrEP Cascade.

(A) All participants. (B) Participants with detectable TFV-DP levels (10+ fmol/punch) at the first Interview. T1: first interview visit (Time point 1). T2: second interview visit (Time point 2). The numbers of participants in the categories of TFV-DP levels are shown in S1 Table. PrEP, pre-exposure prophylaxis; TFV-DP, tenofovir-diphosphate.

The median time between the 2 interviews was 93 (IQR [91, 99]) days. Among AGYW whose TFV-DP levels at enrollment indicated they were taking at least some PrEP (>10 fmol/punch), a high proportion were persistent (52/78: 66.7%, [95% CI 56.2 to 77.1]) (Fig 2B, Table B in S1 Table).

While visit attendance suggested high persistence (Figs 1 and 2B) and self-reported PrEP use was high, actual adherence was low with very few AGYW taking sufficient PrEP to be protected from HIV acquisition. At Interview 1, 298/336 (89%, [95% CI 85 to 92.1]) AGYW reported taking 4 or more (4+) doses in the past 7 days. However, only 21/336 (6.3%, [95% CI 3.7 to 8.8]) had TFV-DP levels consistent with 4+ doses per week (700+ fmol/punch). In fact, although only 20 AGYW (6%, [95% CI 3.4 to 8.5]) reported taking 1 or no doses in the past week, 258/336 (76.8%, [95% CI 72.3 to 81.3]) had TFV-DP levels <10 fmol/punch, which is consistent with no doses in the recent past. Results at Interview 2 were similar. Although most (166/197, 84%, [95% CI 79.2 to 89.3]) of the AGYW who had samples taken at this visit reported taking 4+ doses in the past 7 days, only 9 (4.6%, [95% CI 1.6 to 7.5]) had TFV-DP levels consistent with this level of adherence and 163 (82.7%, [95% CI 77.4 to 88]) had levels consistent with no PrEP use.

PrEP use at the second interview was highly correlated with PrEP use at Interview 1 (S1 Fig). TFV-DP levels greater than 199 fmol/punch (the lower limit of quantification) at Interview 2 were seen almost exclusively among AGYW with levels >199 fmol/punch at Interview 1. Very few AGYW who were not taking PrEP at baseline (TFV-DP <10 fmol/punch) achieved quantifiable levels at Interview 2, and almost all the AGYW who were lost-to-follow up were not taking PrEP at baseline.

Among AGYW who said they discontinued PrEP at Interview 2, primary reasons for discontinuation included stock outs of PrEP, no longer being at risk for HIV (mainly attributed to currently trusting their partner), and returning to school or being away from home (S2 Table). Side effects were also cited fairly frequently as a reason for discontinuation, but reports of discontinuation due to health effects, lifestyle demands, difficulty taking daily pills, pill characteristics, or pressure from partners were not common. Among those who had a late or missed refill visit (N = 49), the most common reasons offered were traveling away from home, forgot the appointment, or no provider was available. Almost all AGYW (179/197, 90.9%) who reported continuing PrEP at Interview 2 said their strong commitment to preventing HIV infection made it easy to take PrEP, and the majority (106/197, 53.8%) said that they had had no difficulty taking PrEP (S3 Table). Only a few (25/197, 13%, [95% CI 8 to 17]) of these AGYW reported not taking any PrEP in the past week. Most (166/197, 84.3%, [95% CI 79.1 to 89.3]) reported taking sufficient (4+) pills to provide protection.

Interestingly, although non-protective TFV-DP levels were detected in almost all participants, most (179/197, 91%) AGYW who said they were continuing PrEP indicated that they were taking PrEP to avoid HIV infection and believed themselves to be protected. At the second interview, participants were asked, “What do you think your chance is of getting HIV?”; only 11/197 (5%) who said they were continuing PrEP answered moderate-to-high chance, in contrast to 38/105 (36%) among discontinuers (S3 Table). AGYW who reported continuing PrEP were then asked, “What would your chance of getting HIV be if you were not taking PrEP?”; 167/197 (85%) answered moderate-to-high.

Despite attending the follow-up and PrEP refill visits and stating that they were continuing PrEP, most PrEP persisters were not adherent. Only 28/176 (16%) had detectable levels at Interview 2, with only 7 (4%) having levels consistent with protection (≥700 fmol/punch). While interventions to improve adherence may benefit these AGYW, it is unclear that such interventions will help the larger group of AGYW who persist in the program without taking PrEP at all. Compared to AGYW who discontinued PrEP, this persistent but non-adherent group (N = 144) was older (adjusted OR 2.13 [95% CI 1.01 to 4.49], p = 0.048), more likely to be active in the DREAMS program (adjusted OR 3.85, [95% CI 1.07 to 13.82], p = 0.039), think they would be at moderate-to-high risk for HIV if not taking PrEP (adjusted OR 10.17, [95% CI 5.14 to 20.13], p < 0.001), and more likely to use injectable contraceptives (adjusted OR 3.28, [95% CI 1.4 to 7.67], p = 0.006) (Table 2).

Table 2

Factors associated with Persistence despite poor adherence (Discontinuers vs. Persisters who did not take PrEP).

	Discontinuers (N = 105)	Persisters taking no PrEP * (N = 144)	Univariable analysis1		Multivariable analysis2
Factor	n	n	Odds ratio OR [95%CI]	p-Value	Odds ratio OR [95% CI]	p-Value
Age ≥22 years	56	100	1.94 [1.1, 3.44]	0.022	2.13 [1.01, 4.49]	0.048
Still active in the DREAMS program	77	132	4.08 [1.74, 9.59]	0.001	3.85 [1.07, 13.82]	0.039
Currently has a sexual partner	100	140	1.72 [0.41, 7.23]	0.456		.
Currently has multiple sex partners	7	23	2.93 [1.09, 7.86]	0.033	2.66 [0.54, 12.97]	0.227
Married/cohabiting	44	67	1.18 [0.71, 1.97]	0.527		.
One or more children	68	110	1.75 [1.06, 2.88]	0.029	0.96 [0.37, 2.51]	0.931
Lives with parents or grandparents	54	68	0.86 [0.48, 1.54]	0.610		.
Lives with partner	43	66	1.2 [0.7, 2.04]	0.507		.
Partner is aware of PrEP use	51	88	1.82 [1.08, 3.06]	0.024	1.95 [0.91, 4.21]	0.088
Partner is very supportive of PrEP use	23	58	2.52 [1.58, 4]	<0.001	2.21 [1.0, 4.88]	0.051
Partner is HIV positive	1	6	4.45 [0.72, 27.37]	0.107		.
Partner has other partners	16	41	2.22 [0.95, 5.16]	0.064	1.13 [0.45, 2.82]	0.796
AGYW believes partner puts her at risk	30	67	2.2 [1.16, 4.18]	0.016	0.84 [0.35, 2.04]	0.698
Moderate-to-high HIV chance if not taking PrEP	38	123	10.25 [5.31, 19.8]	<0.001	10.17 [5.14, 20.13]	<0.001
Experience of intimate partner violence (IPV score >10)	7	10	1.01 [0.39, 2.59]	0.984		.
Depression, moderate to severe	9	10	0.82 [0.37, 1.83]	0.625		.
Social support (most or all the time)	24	27	0.79 [0.45, 1.37]	0.397		.
Inconsistent or no condom use	82	116	1.15 [0.74, 1.78]	0.533		.
Contraceptive use, any	77	109	1.14 [0.64, 2.01]	0.660		.
oral	5	7	1.03 [0.28, 3.7]	0.969		.
injectable	13	30	1.83 [1.01, 3.33]	0.048	3.28 [1.4, 7.67]	0.006
Implant	21	44	1.76 [0.93, 3.34]	0.083	1.55 [0.71, 3.39]	0.274
Male condoms	35	26	0.44 [0.25, 0.78]	0.004	1.04 [0.44, 2.45]	0.935
Female condoms	2	2	0.7 [0.11, 4.4]	0.705		.
Friends are on PrEP	94	138	2.78 [0.73, 10.56]	0.134		.
Told someone of PrEP use since Interview 1	45	76	1.53 [1.06, 2.2]	0.022	0.9 [0.55, 1.47]	0.684
Months since PrEP initiation at Interview 1, 2–3 months	30	37	0.88 [0.44, 1.77]	0.725		.
Months since PrEP initiation at Interview 1, 4–6 months	59	76	0.85 [0.57, 1.28]	0.447		.
Months since PrEP initiation at Interview 1, 6+ months	15	31	1.64 [0.81, 3.32]	0.167		.
Education, primary school	32	46	1.07 [0.61, 1.88]	0.822		.
Education, secondary school	57	85	1.22 [0.68, 2.2]	0.504		.
Education, postsecondary	16	13	0.54 [0.23, 1.31]	0.174		.
Currently in school	45	44	0.57 [0.38, 0.85]	0.006	0.86 [0.47, 1.58]	0.624
In PrEP support group	81	118	1.38 [0.75, 2.54]	0.303		.

* TFV-DP <10 fmol/punch.

1Odds ratio and corresponding p-value were based on univariable generalized estimating equations with logit link function in the model accounting for clustering of study participants within wards.

2Odds ratio and corresponding p-value were based on multivariable generalized estimating equations with logit link function in the model adjusted for county of residence, factors with p-value <0.1 in the univariable analysis as well as clustering of study participants within wards.

AGYW, adolescent girls and young women; PrEP, pre-exposure prophylaxis; TFV-DP, tenofovir-diphosphate.

Among AGYW who persisted in the program, no significant differences were seen between those with TFV-DP levels above versus below 10 fmol/punch in general (S4 Table), likely due to the small number (N = 32) with levels above 10 fmol/punch. Models comparing all persistent AGYW (N = 176) to (1) AGYW who discontinued PrEP (N = 105); and (2) AGYW who attended the second interview but were non-persistent (N = 105 + 21) gave similar results, although the association with partners who were supportive was no longer significant (S5 and S6 Tables).

Discussion

In this study designed to examine PrEP adherence, persistence, and factors associated with persistence, nested within a real-world PrEP program in western Kenya, AGYW had moderate retention in the program, and most reported high adherence and continuation of oral PrEP. However, a minority had detectable TFV-DP at interview visits, and only a small percentage achieved or sustained sufficient drug concentrations to prevent HIV acquisition. Most (85%) continued to receive HIV prevention support through the DREAMS initiative. AGYW who stopped taking PrEP were more likely to have stopped participation in DREAMS (27% versus 8%) and gave a variety of reasons for discontinuation, most of which were not directly related to the PrEP product itself (stockouts, no longer being at risk, returning to school, travel away from the site, etc.). Notably, AGYW who persisted in the PrEP program had a higher self-perceived risk of HIV infection. Among AGYW who reported they were continuing PrEP at the second interview, over 90% indicated the reason was to prevent HIV, although almost all had non-protective TFV-DP levels. This study documents the disconnect between intention and action in a real-world PrEP program and identifies AGYW who may be optimal candidates for long-acting injectable PrEP.

Other studies have observed vast discrepancies between self-reported and objective PrEP adherence measures in clinical trial settings [8,10,33,34]. Importantly, adherence in our study participants was much lower than adherence in AGYW enrolled in clinical trials or in a recent trial of support strategies for oral PrEP in South Africa and Zimbabwe (89% retention at 3 months; 84% of participants tested had detectable TFV-DP) [35,36]. This suggests that oral PrEP adherence among AGYWs in real-world programmatic settings in SSA may be lower than predicted by trial settings and may not assure the drug levels necessary to prevent HIV acquisition. A recent evaluation of the DREAMS Initiative in Kenya and South Africa reported a decline in HIV incidence in AGYW which began prior to DREAMS and which did not accelerate during the first 3 years of the program [37]. Although the reasons for the failure of DREAMS to impact HIV incidence in these locales are unknown, low uptake of interventions by participants may have contributed.

The results of this observational study also provide additional data on the experiences of AGYW using PrEP in a programmatic setting in SSA. Despite their commitment to preventing HIV infection, few AGYW achieved high-level adherence. AGYW who discontinued PrEP use reported multiple reasons for doing so. Although stockouts were most commonly cited, this reason was cited by only a quarter of AGYW who discontinued. Many of the other reasons cited pertained to the PrEP program but had little to do with the PrEP product itself. Few AGYW cited fear of or experience with side effects (15.2% of AGYW who discontinued and 7.6% of those who said they were continuing PrEP). Some AGYW may have engaged in the HIV prevention program, while not adhering to a daily pill regimen, due to social desirability. However, their responses to questions suggest that they were motivated at least in part by perceived HIV risk. The relationship between perceived HIV risk and actual risk in discontinuers versus continuers is complex, as both groups had similar proportions who reported having a sexual partner, living with a partner, using condoms, etc., although continuers were more likely to have multiple partners (7% versus 15%) or to believe that their partner’s behavior put them at risk (29% versus 44%). Only 36% of AGYW who discontinued PrEP reported their current HIV risk as moderate-to-high, although they were not taking PrEP. Only 6% of AGYW who said they were continuing PrEP assessed their current risk as moderate-to-high; a striking 79% said their current risk was low but would be moderate-to-high if they were not taking PrEP. Thus, most AGYW who said they were continuing PrEP acknowledged moderate-to-high HIV risk and the vast majority said they were using PrEP to prevent HIV. The fact that almost none had protective levels implies that these AGYW did not understand or acknowledge that only high-level adherence to daily oral PrEP affords protection.

Overall, these results reveal a group of AGYW who need tailored HIV prevention, including methods such as long-acting injectable PrEP. In our cohort, use of injectable contraception or implants was common. At the second interview, nearly half (45%) of all AGYW and 88% of those using a highly effective contraception method reported use of injectables or implants, which suggests that injections or implants may be acceptable for HIV prevention as well. While attention has focused on improving adherence to oral PrEP, understanding women who are persistent but not adherent and providing them with long-acting formulations may be a more effective way to reduce population-level HIV incidence. In addition, newer prevention modalities will need appropriate behavioral counseling support to assure understanding and correct use.

Limitations of this study include both size and generalizability, as we included a relatively small sample size from a large programmatic project, which may be most generalizable to AGYW in western Kenya. In addition, all AGYW in the study were recruited from the DREAMS initiative and were receiving support for HIV prevention that would likely not be available to them otherwise. Other limitations include potential social desirability bias, recall error in the self-reported data, and possibly remaining confounding bias. A strength was the testing of TFV-DP by LC-MS/MS as an objective measure of adherence. All AGYW participated in face-to-face interviews with a trained counselor. In addition to the self-reported data on factors that might influence PrEP use, we also had access to programmatic data, for example, on pharmacy refills.

In conclusion, our study provides insight into oral PrEP use in a real-world programmatic setting, as well as predictors of PrEP persistence in this context. The results reveal that most AGYW may be better protected by long-acting injectable PrEP than by oral daily PrEP. Future research is needed to clarify whether persistence without adequate adherence is as common among AGYW in other settings, and whether new long-acting PrEP formulations, adequately supported by facilitators identified during use of existing PrEP agents, can afford higher level protection to this very vulnerable population.

STROBE checklist.

(PDF)

Click here for additional data file.

Prospective protocol of the study.

(DOCX)

Click here for additional data file.

Number of participants by TFV-DP levels at Interviews 1 and 2.

(DOCX)

Click here for additional data file.

Reason for stopping PrEP among AGYW reporting PrEP discontinuation and experiences taking PrEP among AGYW reporting PrEP continuation at the second interview.

(DOCX)

Click here for additional data file.

Self-perceived risk for HIV infection among PrEP continuers versus discontinuers.

(DOCX)

Click here for additional data file.

Characteristics of Persisters taking PrEP versus Persisters taking no PrEP at the second interview.

(DOCX)

Click here for additional data file.

Factors associated with Persistence (Discontinuers versus Persisters).

(DOCX)

Click here for additional data file.

Factors associated with Persistence (Non-persisters versus Persisters).

(DOCX)

Click here for additional data file.

TFV-DP levels among study participants at the first interview (Time point 1) and disposition at the time of the second interview (Time point 2).

(DOCX)

Click here for additional data file.

15 Mar 2022

Dear Dr Duerr,

Thank you for submitting your manuscript entitled "Persistence in a PrEP program without protective drug levels is common among adolescent girls and young women in Kenya – would long-acting PrEP formulations serve this population better?" for consideration by PLOS Medicine.

Your manuscript has now been evaluated by the PLOS Medicine editorial staff as well as by an academic editor with relevant expertise and I am writing to let you know that we would like to send your submission out for external peer review.

Before we proceed, please be aware that the in-house editorial staff noted that you conducted research in a foreign country. Please check the relevant national regulations and laws applying to foreign researchers and state whether you obtained the required permits and approvals. PLOS seeks to uphold equity and inclusivity in global health research including authorship. In light of this, please clarify why a local researcher is not a first, second or senior author on this paper, and state measures taken to ensure inclusive participation in the writing of this manuscript. Please ensure authorship criteria is based on the International Committee of Medical Journal Editors (ICMJE) Uniform Requirements for Manuscripts Submitted to Biomedical Journals.

However, before we can send your manuscript to reviewers, we need you to complete your submission by providing the metadata that is required for full assessment. To this end, please login to Editorial Manager where you will find the paper in the 'Submissions Needing Revisions' folder on your homepage. Please click 'Revise Submission' from the Action Links and complete all additional questions in the submission questionnaire.

Please re-submit your manuscript within two working days, i.e. by Mar 17 2022 11:59PM.

Login to Editorial Manager here: https://www.editorialmanager.com/pmedicine

Once your full submission is complete, your paper will undergo a series of checks in preparation for peer review. Once your manuscript has passed all checks it will be sent out for review.

Feel free to email us at plosmedicine@plos.org if you have any queries relating to your submission.

Kind regards,

Beryne Odeny

PLOS Medicine

20 Apr 2022

Dear Dr. Duerr,

Thank you very much for submitting your manuscript "Persistence in a PrEP program without protective drug levels is common among adolescent girls and young women in Kenya – would long-acting PrEP formulations serve this population better?" (PMEDICINE-D-22-00813R1) for consideration at PLOS Medicine.

Your paper was evaluated by a senior editor and discussed among all the editors here. It was also discussed with an academic editor with relevant expertise, and sent to independent reviewers, including a statistical reviewer.

Considering these reviews, we would be grateful if you could please revise your manuscript to respond to comments raised by reviewers. We would strongly recommend that you pay special attention to the statistical reviewers’ comments. Please note that this is not a guarantee that we will accept the manuscript and that further consideration is dependent on the submission of a manuscript that addresses all reviewer concerns. We will carefully review your manuscript upon revision, so please ensure that your revision is thorough.

The reviews are appended at the bottom of this email and any accompanying reviewer attachments can be seen via the link below:

[LINK]

In light of these reviews, I am afraid that we will not be able to accept the manuscript for publication in the journal in its current form, but we would like to consider a revised version that addresses the reviewers' and editors' comments. Obviously we cannot make any decision about publication until we have seen the revised manuscript and your response, and we plan to seek re-review by one or more of the reviewers.

In revising the manuscript for further consideration, your revisions should address the specific points made by each reviewer and the editors. Please also check the guidelines for revised papers at http://journals.plos.org/plosmedicine/s/revising-your-manuscript for any that apply to your paper. In your rebuttal letter you should indicate your response to the reviewers' and editors' comments, the changes you have made in the manuscript, and include either an excerpt of the revised text or the location (eg: page and line number) where each change can be found. Please submit a clean version of the paper as the main article file; a version with changes marked should be uploaded as a marked up manuscript.

In addition, we request that you upload any figures associated with your paper as individual TIF or EPS files with 300dpi resolution at resubmission; please read our figure guidelines for more information on our requirements: http://journals.plos.org/plosmedicine/s/figures. While revising your submission, please upload your figure files to the PACE digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email us at PLOSMedicine@plos.org.

We expect to receive your revised manuscript by May 11 2022 11:59PM. Please email us (plosmedicine@plos.org) if you have any questions or concerns.

***Please note while forming your response, if your article is accepted, you may have the opportunity to make the peer review history publicly available. The record will include editor decision letters (with reviews) and your responses to reviewer comments. If eligible, we will contact you to opt in or out.***

We ask every co-author listed on the manuscript to fill in a contributing author statement, making sure to declare all competing interests. If any of the co-authors have not filled in the statement, we will remind them to do so when the paper is revised. If all statements are not completed in a timely fashion this could hold up the re-review process. If new competing interests are declared later in the revision process, this may also hold up the submission. Should there be a problem getting one of your co-authors to fill in a statement we will be in contact. YOU MUST NOT ADD OR REMOVE AUTHORS UNLESS YOU HAVE ALERTED THE EDITOR HANDLING THE MANUSCRIPT TO THE CHANGE AND THEY SPECIFICALLY HAVE AGREED TO IT. You can see our competing interests policy here: http://journals.plos.org/plosmedicine/s/competing-interests.

Please use the following link to submit the revised manuscript:

https://www.editorialmanager.com/pmedicine/

Your article can be found in the "Submissions Needing Revision" folder.

To enhance the reproducibility of your results, we recommend that you deposit your laboratory protocols in protocols.io, where a protocol can be assigned its own identifier (DOI) such that it can be cited independently in the future. Additionally, PLOS ONE offers an option to publish peer-reviewed clinical study protocols. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols

Please ensure that the paper adheres to the PLOS Data Availability Policy (see http://journals.plos.org/plosmedicine/s/data-availability), which requires that all data underlying the study's findings be provided in a repository or as Supporting Information. For data residing with a third party, authors are required to provide instructions with contact information for obtaining the data. PLOS journals do not allow statements supported by "data not shown" or "unpublished results." For such statements, authors must provide supporting data or cite public sources that include it.

We look forward to receiving your revised manuscript.

Sincerely,

Beryne Odeny,

PLOS Medicine

plosmedicine.org

-----------------------------------------------------------

Requests from the editors:

1) Please revise your title according to PLOS Medicine's style. Your title must be nondeclarative and not a question. It should begin with main concept if possible. Please place the study design in the subtitle (i.e., after a colon), e.g., a prospective cohort study.

2) Please include line numbers in your next draft.

3) Under the list of authors please include a footnote that indicates that the first 3 authors are joint first authors, in keeping with your prior request to make them co-/first authors.

4) The Data Availability Statement (DAS) requires revision. For each data source used in your study:

a) If the data are owned by a third party but freely available upon request, please note this and state the owner of the data set and contact information for data requests (web or email address). Note that a study author cannot be the contact person for the data.

b) If the data are not freely available, please describe briefly the ethical, legal, or contractual restriction that prevents you from sharing it. Please also include an appropriate contact (web or email address) for inquiries (again, this cannot be a study author).

5) Abstract:

a) Please structure your abstract using the PLOS Medicine headings (Background, Methods and Findings, Conclusions).

i) Please combine the Methods and Findings sections into one section, “Methods and findings”.

ii) The interpretation should be renamed “Conclusions”

b) Please include years during which the study took place

c) Please include the important dependent variables that are adjusted for in the analyses.

d) Please ensure that all numbers presented in the abstract are present and identical to numbers presented in the main manuscript text.

e) Please quantify the main results (please present both 95% CIs and p values).

f) In the last sentence of the Abstract Methods and Findings section, please describe the main limitation(s) of the study's methodology.

g) Please remove “funding” statement

6) At this stage, we ask that you include a short, non-technical Author Summary of your research to make findings accessible to a wide audience that includes both scientists and non-scientists. The Author Summary should immediately follow the Abstract in your revised manuscript. This text is subject to editorial change and should be distinct from the scientific abstract. Please see our author guidelines for more information: https://journals.plos.org/plosmedicine/s/revising-your-manuscript#loc-author-summary

7) Introduction:

a) Please remove the description of the methods from the last paragraph, i.e., “we examine PrEP use cascade… refill data from the DREAMS database.” This can be moved to the Methods section.

b) Please conclude the Introduction with a clear description of the study question or hypothesis.

8) Did your study have a prospective protocol or analysis plan? Please state this (either way) early in the Methods section.

a) If a prospective analysis plan (from your funding proposal, IRB or other ethics committee submission, study protocol, or other planning document written before analyzing the data) was used in designing the study, please include the relevant prospectively written document with your revised manuscript as a Supporting Information file to be published alongside your study, and cite it in the Methods section. A legend for this file should be included at the end of your manuscript.

b) If no such document exists, please make sure that the Methods section transparently describes when analyses were planned, and when/why any data-driven changes to analyses took place.

c) In either case, changes in the analysis-- including those made in response to peer review comments-- should be identified as such in the Methods section of the paper, with rationale.

9) Please ensure that the study is reported according to the STROBE and include the completed STROBE checklist as Supporting Information. Please add the following statement, or similar, to the Methods: "This study is reported as per the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guideline (S1 Checklist)."

a) When completing the checklist, please use section and paragraph numbers, rather than page numbers.

10) Statistical analysis

a) Please include adjustment variables.

b) Please adjust for clustering at individual and facility level.

11) Please provide p values in addition to 95% CIs in the main text and tables

12) Please define all abbreviations in Tables and Figures e.g., PrEP, LTFU, TFV-DP, DBS, AGYW

13) Please indicate in the figure caption the meaning of the bars and whiskers in Figure S1.

14) Please replace the term “condom users” with “AGYW who use condoms”

15) Please remove the ‘Declaration of interest statement” and “Data sharing” from the end of the main text. In the event of publication, this information will be published as metadata based on your responses to the submission form.

16) References:

a) Please select the PLOS Medicine reference style in your citation manager. In-text reference call outs should be presented as follows noting the absence of spaces within the square brackets, e.g., "... services [1,2]."

b) References should have six names before et al. For those with more than six names, please ensure that et al., is inserted after six names

c) Please ensure that journal name abbreviations consistently match those found in the National Center for Biotechnology Information (NCBI) databases. https://journals.plos.org/plosmedicine/s/submission-guidelines#loc-references.

d) Ref #20 is incomplete

Comments from the reviewers:

Reviewer #1: The manuscript by Tabsoba, et al. report on the "real-world" use of oral PrEP among AGYW in two counties in western Kenya with a high incidence of HIV. Please see my detailed comments below about each section.

Introduction:

* The statement on new HIV infections in the two countries comes from a 2015 reference, seven years ago. The authors should update this number with a more recent reference.

* I would not consider the 3-month visit "long-term adherence"

* How were the 336 participants selected from the larger group in the DREAMS PrEP program—either explain in introduction, or remove this detail and leave for the methods section

Methods:

* This sentence doesn't make sense to me: "and a two-level factor potentially associated with PrEP adherence."

* I realize that this study was conducted in a real-world setting, but anticipating a 50% loss to follow-up is very high

* I'm confused about the methods of sampling. In one section it is mentioned that a random sample was obtained from the original enrolled cohort in the DREAMS PrEP program. However, the methods used to randomly sample are not provided. Secondly, a flow chart would help the reader to assess what happened along the enrolment cascade, who was subsequently excluded from the analysis (e.g. they failed to return for follow-up, and/or didn't report taking PrEP) would be tremendously helpful. In the Results section (first paragraph) there is new mention about who was eligible—higher risk sexual behaviors. This information makes once think that random sampling was not deployed. I think that these are the criteria that were used to enroll the DREAMS cohort, but can't be certain. Again, this section should be in the Methods not the Results section.

Results:

* "Kisumu, the remainder in Homa Bay." Does this refer to the city/town or counties?

* "PrEP program for a mean of 142 days." Provide SD—or is median a better measure with IQR?

* Throughout Results it would be helpful to the reader to provide the Ns along with the percentages.

* "PrEP persistence," not sure this is the standard designation in the literature

* Suggest adding "among" to "in contrast to 38/105 (36%) 'among' discontinuers."

* Table 1 has quite several errors—second column is not all %s, use of "****", etc. It also could benefit from reformatting

* Why was the US Household Security Survey used? The validated HFIAS has been used repeatedly in the same population in western Kenya

* I'm not sure that Figure 2 adds much more than what is stated in the narrative

Discussion:

* The discussion section is well written in general, with adequate references to substantiate the relevance of the new data from the study. In addition, the authors do spell out some of the weaknesses, while acknowledging its strengths. My primary concern is with generalizability of these data, based on some of the weaknesses I identified with the methods, or at least the description of the methods used.

Reviewer #2: Statistical review

This paper reports an observational study that investigates factors associated with persistence in a PrEP programme amongst adolescent girls and young women. I had some comments on the statistical methods/reporting of the study:

1. Abstract "samples taken at the second visit" - it might be useful if the same language as the previous sentence is used - is second visit the same as the second interview or the interim refill visit?

2. Methods, analysis "Persistent AGYW were defined as having attended both interviews as well as interim visits for PrEP refills and stating that they were taking PrEP at both interviews. Those lost to follow up between visits were excluded from analysis." - I found this confusing whether those lost to follow-up were included as non-persistent or excluded, or is this saying that only persistent AGYW were included in analysis? If loss to follow-up led to exclusion, this seems to mean an important set of likely non-persisters was excluded?

3. Methods, analysis: can more be said about what characteristics were considered for the model - is it the ones in study procedures? Some of these wouldn't vary between visit 1 and visit 2 but others would - I wasn't sure why visit 2 characteristics were used instead of visit 1 characteristics? Using visit 1 characteristics would strike me as being more about predicting which participants are persistent.

4. Methods, analysis: can more be added about the stepwise procedures used to build the model (including rules for adding/deleting variables), perhaps in supplementary material? Standard approaches such as forward or backward selection have been criticised so it would be good if more than 1 approach led to the same variables being included, to demonstrate robustness. It may be worth considering a sparse regression approach to supplement this analysis.

5. Methods, analysis: in the results, censored individuals are mentioned - presumably these were excluded from analysis?

6. Table 2 and Figure 2 - I didn't follow why the p-values were calculated comparing discontinuers and persisters who were taking no PrEP. This doesn't seem consistent with the hypothesis that the study was powered for in the sample size calculation: factors related to PrEP adherence.

7. I think Figure S1 would be better included in the main paper.

James Wason

Reviewer #3: Thank you for the opportunity to review this manuscript that describes an assessment of PrEP adherence in 336 AGYW participating in a DREAMS programme in Western Kenya who attended two study visits.

Major comments

1. The manuscript would benefit from a figure that shows the study design and or the attrition of participants at each step of the analysis. Participants appear to be excluded at certain points but the rationale for non-inclusion was not entirely clear as those with some information may provide important insights.

2. The primary outcome appears to be PrEP adherence defined as TDF/FTC levels on DBS >700f/ml per punch. The authors appear to use a variety of cut-offs however and it is not always clear how these were chosen. In the methods it would be helpful to provide a brief summary of the cut offs and the reasons selected based on published evidence as well as how these correspond with dosing (and limitations given largely based on MSM data). DBS reflects use in the past 4 weeks, but cut-offs may vary depending on whether this is first 4 weeks of use or not. The authors may want to be more clear about these time frames and the relation between outcome assessments and timeframes for reporting exposures/factors associated with adherence.

3. The authors argue that they have defined a PrEP cascade; however the definitions are somewhat different to definitions published by other authors on the PrEP cascade. It would be helpful if the authors could better define the process of the DREAMS PrEP programme, e.g. how initiation occurs, how often refills are given, frequency of HIV testing etc. Then the authors can locate their study on top of this framework and provide their definition of persistence which appears to be related to study visits primarily, with the requirement to return for at least one PrEP refill. The authors could perhaps explain why visits were not aligned with PrEP refill visits for AGYW as that could assist with anchoring their recall/reporting better perhaps. The authors may wish to include a brief review of PrEP cascades in the introduction to underpin their choice of terminology or methods.

4. The authors use several measures in the baseline assessment as well as for assessments at the second visit. These are not defined in the methods but only as footnotes to tables. It would be helpful to define these measures more clearly in the methods section and reasons for use/validation of these measures in adolescent populations in sub-Saharan Africa. For example, is it appropriate to use a US-based food security measure in the Kenyan context? When defining measures add scales, cut-offs and whether or not validated in this or similar young African populations.

5. The authors do not describe the package of interventions offered to AGYW to support their PrEP adherence apart from a brief mention in table 1 regarding a PrEP support group. There is value in understanding what if any adherence support interventions were offered and how they aligned with PrEP refill visits to provide context to the environment in which PrEP was offered.

6. The authors used an interviewer administered tool to solicit information from participants. Could they comment further of strategies to minimise social desirability bias. The participants seem to understand that they were being interviewed about their PrEP use. The authors observe the difference between reported and actual actions, but do not comment on the potential bias induced by the data collection process.

7. In the discussion, the authors appear to discount reasons for non-PrEP use as not related to PrEP. However in reviewing table S2 it appears that many of the reasons for discontinuation are supply side or programmatic issues e.g. stock outs, lack of access because travelled from PrEP refill site or returned to school. In addition, side effects may also be an issue with poor counselling for those who are in early PrEP start up. The aggregation of PrEP users at different stages of PrEP use (less/more experienced) makes it challenging to tease apart some of these issues.

8. There are very few observations in the manuscript around the social and structural barriers to PrEP access for these young participants e.g. 17% experience IPV, 12% have adequate social support, 75% have food insecurity, most are married and have children and live in multi-generational homes. It is true that the data confirms that participants are motivated to use PrEP but are not able to act on those intentions perhaps because of the more pressing concerns in their life. It would be helpful if the authors could reflect on how these upstream factors may influence the direct factors observed to be associated with lack of persistence.

9. At times the sections bled into one another, methods in the results section, results in the discussion and discussion in results. The manuscript would benefit from a thorough edit to define each section more clearly and to make it easier for the reader to follow the arguments being made with the data.

10. In table 2, it is not clear what the P-value refers to (although the heading defines persisters vs continuers). Please clarify which comparison the p-value refers to with respect to the persister column, since those with detectable vs non-detectable PrEP appear quite different. It may be more helpful to present an analysis of continuers vs. discontinuers to understand barriers to PrEP continuation, and then to explore reasons for non-adherence which may not be the same as those for continuation and may require other interventions to address. Long-acting agents may help with the adherence issue, but may still be perplexed with the discontinuation challenge.

11. T

Minor comments

12. Abstract: define the outcome measures and cut offs for DBS as well as the assay in the methods, and the definitions used for levels consistent with no dosing/levels associated with protection.

13. Abstract: define the persistence outcome in the methods of the abstract

14. Abstract: the conclusion states that this analysis identifies AGYW who may benefit from LA PrEP but it is not entirely clear from the findings how this population are identified without the use of a drug level assessment. Please clarify

15. Introduction: TDF/FTC = tenofovir disoproxil fumarate/emtricitabine. Please spell out in full

16. Introduction: the authors should mention the PK requirement for near perfect PrEP dosing in women which may compound challenges with adherence and are different for MSM at least.

17. Introduction: please provide references for obstacles to adherence support in para 1 e.g. lack of partner support.

18. Introduction: CAB LA was evaluated in cisgender men and transgender women who has sex with men in the Americas, Thailand and South Africa and both HPTN 083 and 084 showed that CAB LA was superior to TDF/FTC for HIV prevention.

19. Introduction: clarify that plasma TDF/FTC was detectable in a random subset 56% of samples in HPTN 084 in women who had a median follow up of 1.2 years. The time frame seems relevant. In addition, injection coverage was across both arms of the study not just the CAB LA group. The sentence about visit attendance vs adherence probably needs to conclude this paragraph

20. Introduction: define persistence in relation to literature

21. Introduction: consider introducing a summary of the notion of a PrEP cascade and mention of the concept of Prevention effective adherence

22. Introduction: final comment appears to bleed into methods and may be better as a framing of objectives with definitions in methods

23. Methods: would benefit from a figure that summarises time on PrEP and relation to sample collection and two visits/could summarise the reasons for inclusion/exclusion from analysis at each step of design

24. Methods: when defining measures add scales, cut-offs and whether or not validated in this or similar young African populations

25. Methods: what was the interval between study visits?

26. Results: para 1; a description of the DREAMS PrEP programme including eligibility criteria for PrEP may be better in the methods since the reasons for non-inclusion are not related to these criteria it seems.

27. Results: can you provide some distribution of where respondents were in their PrEP journey with respect to the mean 142 days of PrEP? What % were in first month, months 2-3, months 3-6 as it might relate to a PrEP programme. This makes it easier then also to overlay where discontinuation might be happening.

28. Results: what was the mean interval between study visits?

29. Results: para 2 provide numerator, denominator and percentages so that it is possible to follow the logic of which group is being discussed.

30. Results: clarify lower limit of quantification stated as >199 f/mol per punch - this seems to contradict other statements and measures and may not be correct. Should this be defined in the methods?

31. Results: para that begins " Thus it seems…" seems to be editorial commentary and may be better as a comment in the discussion with a focus on presenting the outcomes in the results.

32. Discussion: its not clear what data support the statement that programme retention was good.

33. Discussion: the clinical trial referred to in para 2 was not a trial of PrEP but an assessment of uptake and acceptability and included an evaluation of adherence strategies. Perhaps the difference is not real world vs. not real word but the focus on adherence support for an adolescent population.

34. Discussion: para 3, not clear what data support the statement that this shows a cascade of care in the sense of how cascades have been described in the literature. May need to refine or clarify.

35. Discussion: the authors mention that they had access to pharmacy refill data. It would be helpful to summarise these for the cohort and present in relation to when they were interviewed. The refill data are mentioned but data are not presented systematically.

36. References: update to reflect published manuscripts where possible; some conference abstracts are referred to when in fact peer-reviewed manuscripts are available.

Any attachments provided with reviews can be seen via the following link:

[LINK]

7 Jun 2022

Submitted filename: Response to reviewers final.docx

Click here for additional data file.

21 Jul 2022

Dear Dr. Duerr,

Thank you very much for re-submitting your manuscript "Continued attendance in a PrEP program despite low adherence and non-protective drug levels among adolescent girls and young women in Kenya: results from a prospective cohort study" (PMEDICINE-D-22-00813R2) for review by PLOS Medicine.

I have discussed the paper with my colleagues and the academic editor and it was also seen again by one reviewer. I am pleased to say that provided the remaining editorial and production issues are dealt with we are planning to accept the paper for publication in the journal.

The remaining issues that need to be addressed are listed at the end of this email. Any accompanying reviewer attachments can be seen via the link below. Please take these into account before resubmitting your manuscript:

[LINK]

***Please note while forming your response, if your article is accepted, you may have the opportunity to make the peer review history publicly available. The record will include editor decision letters (with reviews) and your responses to reviewer comments. If eligible, we will contact you to opt in or out.***

In revising the manuscript for further consideration here, please ensure you address the specific points made by each reviewer and the editors. In your rebuttal letter you should indicate your response to the reviewers' and editors' comments and the changes you have made in the manuscript. Please submit a clean version of the paper as the main article file. A version with changes marked must also be uploaded as a marked up manuscript file.

Please also check the guidelines for revised papers at http://journals.plos.org/plosmedicine/s/revising-your-manuscript for any that apply to your paper. If you haven't already, we ask that you provide a short, non-technical Author Summary of your research to make findings accessible to a wide audience that includes both scientists and non-scientists. The Author Summary should immediately follow the Abstract in your revised manuscript. This text is subject to editorial change and should be distinct from the scientific abstract.

We expect to receive your revised manuscript within 1 week. Please email us (plosmedicine@plos.org) if you have any questions or concerns.

We ask every co-author listed on the manuscript to fill in a contributing author statement. If any of the co-authors have not filled in the statement, we will remind them to do so when the paper is revised. If all statements are not completed in a timely fashion this could hold up the re-review process. Should there be a problem getting one of your co-authors to fill in a statement we will be in contact. YOU MUST NOT ADD OR REMOVE AUTHORS UNLESS YOU HAVE ALERTED THE EDITOR HANDLING THE MANUSCRIPT TO THE CHANGE AND THEY SPECIFICALLY HAVE AGREED TO IT.

Please ensure that the paper adheres to the PLOS Data Availability Policy (see http://journals.plos.org/plosmedicine/s/data-availability), which requires that all data underlying the study's findings be provided in a repository or as Supporting Information. For data residing with a third party, authors are required to provide instructions with contact information for obtaining the data. PLOS journals do not allow statements supported by "data not shown" or "unpublished results." For such statements, authors must provide supporting data or cite public sources that include it.

To enhance the reproducibility of your results, we recommend that you deposit your laboratory protocols in protocols.io, where a protocol can be assigned its own identifier (DOI) such that it can be cited independently in the future. Additionally, PLOS ONE offers an option to publish peer-reviewed clinical study protocols. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript.

Please note, when your manuscript is accepted, an uncorrected proof of your manuscript will be published online ahead of the final version, unless you've already opted out via the online submission form. If, for any reason, you do not want an earlier version of your manuscript published online or are unsure if you have already indicated as such, please let the journal staff know immediately at plosmedicine@plos.org.

If you have any questions in the meantime, please contact me or the journal staff on plosmedicine@plos.org.

We look forward to receiving the revised manuscript by Jul 28 2022 11:59PM.

Sincerely,

Beryne Odeny,

PLOS Medicine

plosmedicine.org

------------------------------------------------------------

Requests from Editors:

1. Abstract: please include the important dependent variables that are adjusted for in the analyses.

2. Author summary: please quantify the main results with actual amounts or percentages

3. Prospective protocol:

a) In the Methods, please indicate whether this study had a prospective protocol and identify changes that were made in this analysis including those in response to peer review.

b) Please include the relevant prospectively written document with your revised manuscript as a Supporting Information file to be published alongside your study and cite it in the Methods section. A legend for this file should be included at the end of your manuscript.

Comments from Reviewers:

Reviewer #2: Thank you to the authors for addressing my previous comments well. All the issues I raised were addressed/justified and I have no further issues to raise.

Any attachments provided with reviews can be seen via the following link:

[LINK]

12 Aug 2022

Dear Dr. Duerr,

Thank you very much for re-submitting your manuscript "Continued attendance in a PrEP program despite low adherence and non-protective drug levels among adolescent girls and young women in Kenya: results from a prospective cohort study" (PMEDICINE-D-22-00813R3) for review by PLOS Medicine.

I have discussed the paper with my colleagues and I am pleased to say that provided the remaining editorial and production issues are dealt with we are planning to accept the paper for publication in the journal.

The remaining issues that need to be addressed are listed at the end of this email. Any accompanying reviewer attachments can be seen via the link below. Please take these into account before resubmitting your manuscript:

[LINK]

***Please note while forming your response, if your article is accepted, you may have the opportunity to make the peer review history publicly available. The record will include editor decision letters (with reviews) and your responses to reviewer comments. If eligible, we will contact you to opt in or out.***

In revising the manuscript for further consideration here, please ensure you address the specific points made by each reviewer and the editors. In your rebuttal letter you should indicate your response to the reviewers' and editors' comments and the changes you have made in the manuscript. Please submit a clean version of the paper as the main article file. A version with changes marked must also be uploaded as a marked up manuscript file.

Please also check the guidelines for revised papers at http://journals.plos.org/plosmedicine/s/revising-your-manuscript for any that apply to your paper. If you haven't already, we ask that you provide a short, non-technical Author Summary of your research to make findings accessible to a wide audience that includes both scientists and non-scientists. The Author Summary should immediately follow the Abstract in your revised manuscript. This text is subject to editorial change and should be distinct from the scientific abstract.

We expect to receive your revised manuscript within 1 week. Please email us (plosmedicine@plos.org) if you have any questions or concerns.

We ask every co-author listed on the manuscript to fill in a contributing author statement. If any of the co-authors have not filled in the statement, we will remind them to do so when the paper is revised. If all statements are not completed in a timely fashion this could hold up the re-review process. Should there be a problem getting one of your co-authors to fill in a statement we will be in contact. YOU MUST NOT ADD OR REMOVE AUTHORS UNLESS YOU HAVE ALERTED THE EDITOR HANDLING THE MANUSCRIPT TO THE CHANGE AND THEY SPECIFICALLY HAVE AGREED TO IT.

Please ensure that the paper adheres to the PLOS Data Availability Policy (see http://journals.plos.org/plosmedicine/s/data-availability), which requires that all data underlying the study's findings be provided in a repository or as Supporting Information. For data residing with a third party, authors are required to provide instructions with contact information for obtaining the data. PLOS journals do not allow statements supported by "data not shown" or "unpublished results." For such statements, authors must provide supporting data or cite public sources that include it.

To enhance the reproducibility of your results, we recommend that you deposit your laboratory protocols in protocols.io, where a protocol can be assigned its own identifier (DOI) such that it can be cited independently in the future. Additionally, PLOS ONE offers an option to publish peer-reviewed clinical study protocols. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript.

Please note, when your manuscript is accepted, an uncorrected proof of your manuscript will be published online ahead of the final version, unless you've already opted out via the online submission form. If, for any reason, you do not want an earlier version of your manuscript published online or are unsure if you have already indicated as such, please let the journal staff know immediately at plosmedicine@plos.org.

If you have any questions in the meantime, please contact me or the journal staff on plosmedicine@plos.org.

We look forward to receiving the revised manuscript by Aug 19 2022 11:59PM.

Sincerely,

Beryne Odeny,

PLOS Medicine

plosmedicine.org

------------------------------------------------------------

Requests from Editors:

1. Author summary: Please provide estimates as amounts and percentages. Please do not use coefficients and p-values in the author summary as this is supposed to be a non-technical summary for a general audience.

Any attachments provided with reviews can be seen via the following link:

[LINK]

19 Aug 2022

Dear Dr Duerr,

On behalf of my colleagues and the Academic Editor, Dr. Marie-Louise Newell, I am pleased to inform you that we have agreed to publish your manuscript "Continued attendance in a PrEP program despite low adherence and non-protective drug levels among adolescent girls and young women in Kenya: results from a prospective cohort study" (PMEDICINE-D-22-00813R4) in PLOS Medicine.

Before your manuscript can be formally accepted you will need to complete some formatting changes, which you will receive in a follow up email. Please be aware that it may take several days for you to receive this email; during this time no action is required by you. Once you have received these formatting requests, please note that your manuscript will not be scheduled for publication until you have made the required changes.

In the meantime, please log into Editorial Manager at http://www.editorialmanager.com/pmedicine/, click the "Update My Information" link at the top of the page, and update your user information to ensure an efficient production process.

PRESS

We frequently collaborate with press offices. If your institution or institutions have a press office, please notify them about your upcoming paper at this point, to enable them to help maximise its impact. If the press office is planning to promote your findings, we would be grateful if they could coordinate with medicinepress@plos.org. If you have not yet opted out of the early version process, we ask that you notify us immediately of any press plans so that we may do so on your behalf.

We also ask that you take this opportunity to read our Embargo Policy regarding the discussion, promotion and media coverage of work that is yet to be published by PLOS. As your manuscript is not yet published, it is bound by the conditions of our Embargo Policy. Please be aware that this policy is in place both to ensure that any press coverage of your article is fully substantiated and to provide a direct link between such coverage and the published work. For full details of our Embargo Policy, please visit http://www.plos.org/about/media-inquiries/embargo-policy/.

To enhance the reproducibility of your results, we recommend that you deposit your laboratory protocols in protocols.io, where a protocol can be assigned its own identifier (DOI) such that it can be cited independently in the future. Additionally, PLOS ONE offers an option to publish peer-reviewed clinical study protocols. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols

Thank you again for submitting to PLOS Medicine. We look forward to publishing your paper.

Sincerely,

Beryne Odeny, PhD

PLOS Medicine