Predictors of self-reported symptoms and testing for COVID-19 in Canada using a nationally representative survey.

Random population-based surveys to estimate prevalence of SARS-CoV2 infection causing coronavirus disease (COVID-19) are useful to understand distributions and predictors of the infection. In April 2020, the first-ever nationally representative survey in Canada polled 4,240 adults age 18 years and older about self-reported COVID experience in March, early in the epidemic. We examined the levels and predictors of COVID symptoms, defined as fever plus difficulty breathing/shortness of breath, dry cough so severe that it disrupts sleep, and/or loss of sense of smell; and testing for SARS-CoV-2 by respondents and/or household members. About 8% of Canadians reported that they and/or one or more household members experienced COVID symptoms. Symptoms were more common in younger than in older adults, and among visible minorities. Overall, only 3% of respondents and/or household members reported testing for SARS-CoV-2. Being tested was associated with having COVID symptoms, Indigenous identity, and living in Quebec. Periodic nationally representative surveys of symptoms, as well as SARS-CoV-2 antibodies, are required in many countries to understand the pandemic and prepare for the future.

Introduction

The pandemic of SARS-CoV-2 infection causing coronavirus disease-2019 (COVID-19, hereafter “COVID”) has affected almost every country globally [1]. Understanding the socio-demographic characteristics of COVID patients can inform efforts to reduce transmission [2]. In Canada and other high-income country settings where reliable data can be gathered, a combination of population-based surveys (including surveys and testing), hospitalizations, and mortality data can produce an accurate profile of the impact of the pandemic.

Here, we report on the results of the first nationally-representative poll in Canada of self-reported COVID symptoms conducted by the Angus Reid Forum in early April 2020 covering symptoms reported mostly in March 2020, prior to the peak month of test-reported cases in April. Specifically, we seek to understand the distribution and predictors of Canadians reporting possible COVID symptoms and testing for SARS-CoV-2 using the current standard (polymerase chain reaction or PCR-based) test. We discuss these findings in the context of the age distribution of COVID hospitalizations and deaths, and a planned survey of antibodies to SARS-CoV-2 in a random sample of Canadians.

Materials and methods

Study design

The Angus Reid Institute (ARI) conducted an online survey from April 1–5, 2020, among a nationally representative randomized sample of 4,240 Canadian adults who are members of Angus Reid Forum, drawing upon 70,000 adults in a distributed online panel used for policy research by public sector, not-for-profit, media and commercial organizations (with sampling units approximately corresponding to each federal riding) [3]. A probability sample of this size carries a margin of error of +/- 2 percentage points, 19 times out of 20. The sample frame was established to match the Canadian census data from Statistics Canada [4]. The survey was commissioned and paid for by ARI. Respondents were required to be 18 years or older and to speak English or French.

Overall, the survey respondents were broadly representative of Canadian society in terms of gender, age, regional distribution, and numbers of household members (Table 1). Survey respondents were less representative of Canada in terms of ethnicities other than Indigenous. The survey had fewer single-member households than in the Canadian census, and had slightly higher education levels than did the 2019 Canadian population.

Table 1

Socio-demographic characteristics of respondents (n = 4,240) as compared to the Canadian population in 2019.

Characteristics	Completed survey, sample size		Canadian population, 2019* (%) [4, 5]
	n	%
Gender
Male	2017	47.9	49.4
Female	2205	52.0	50.6
Other†	18	0.4
Age group
18–45 years	2007	47.3	46.4
46–65 years	1511	35.6	33.4
66+ years	722	17.0	20.2
Education
High school and under	1064	25.1	35.2
Some college/university and higher	3176	74.9	64.8
Visible minority‡
No	3686	86.9	71.4
Yes	554	13.1	28.7
Number of household members
Lived alone	672	15.9	28.2
Two people	1615	38.1	34.4
Three people	804	19.0	15.2
Four or more people	1149	27.1	22.2
Ethnicity
Indigenous§	226	5.3	5.0
English and other European	3567	84.1	73.1
Others|	365	8.6	22.0
Rather Not Say	82	1.9
Province/region
Ontario	1600	37.7	38.9
British Columbia	554	13.1	13.8
Quebec	1020	24.1	22.7
Alberta	475	11.2	11.2
Manitoba	150	3.5	3.5
Saskatchewan	133	3.1	3.0
Atlantic provinces	308	7.3	6.6

*All comparisons are from the 2016 Census, except Province/region which is from 2019 Statistics Canada population data [4].

†“Other” gender includes genders that neither male nor females.

‡Visible minority is defined as persons, other than Indigenous peoples, who are non-white in race or non-white in colour) [6].

§Indigenous populations including First Nations, Inuit, or Métis.

|“Others” ethnicity includes Caribbean, Central or South American, African, Middle Eastern, Central Asian, Chinese, Filipino, South Asian, other Asian, and Oceania.

Survey questionnaire and data collection

The survey questionnaire included questions related to COVID and socio-demographic characteristics among both the respondents and members of their households. Questions related to COVID symptoms included whether the respondent experienced any of a list of eight symptoms: i) difficulty breathing or shortness of breath, ii) a fever, iii) a mild dry cough, iv) a severe dry cough so severe that it disrupts sleep, v) sore throat, vi) frequent sneezing, vii) loss of sense of smell, viii) fever with hallucinations over the past month. Questions related to testing for COVID included whether the respondent have been tested for COVID, scheduled to be tested, trying to get tested but have not been able to, have done a self-assessment through government website/app, or have not been tested nor planning to be tested or self-assessed. Respondents living in households with more than one person were also asked if anyone else in the household had experienced any of the COVID symptoms and have been tested for COVID. The questionnaire used for this study was developed based on expert opinion, and the choice of COVID symptoms were based on expert opinion and physicians from Unity Health Toronto. The full survey questionnaire is provided in the (S1 Appendix). The survey instrument was pre-tested in 60 individuals prior to the main survey.

The data were collected by Angus Reid Institute and were analysed at Angus Reid Institute and Centre for Global Health Research, Unity Health Toronto. All personal identifiers were removed from the collected data and each participant was then assigned a randomly-generated code identifier before analysis.

Analysis

To understand the socio-demographic predictors of COVID symptoms, we conducted a logistic regression analysis where the outcome was self-reported symptoms suggestive of COVID infection which we defined in this study as the respondent reporting himself/herself and/or at least one member of the household having had a combination of fever (with or without hallucinations) and any of i) difficulty breathing/shortness of breath or ii) dry cough so severe that it disrupts sleep or iii) a loss of a sense of smell in the past month; and the explanatory variables were gender (male, female, or other), education level (high school and under, or some college/university and higher), province, age, ethnicity (Indigenous, English and other European, or others), visible minority (defined as persons, other than Aboriginal peoples, who are non-white in race or colour) [6], and number of household members. We defined Indigenous ethnicity as whether the person reported identifying with the Aboriginal peoples of Canada which includes First Nations, Métis or Inuit and/or those who reported Registered or Treaty Indian status [7]. We also used logistic regression analysis to identify predictors of testing, which included the above explanatory variables and also COVID symptoms in the respondent or a household member. Respondents were considered “tested” if he/she had been tested or were scheduled to be tested. Respondents who did not report on any of the explanatory variables were excluded from these analyses. Results of the regression analyses were presented after adjusting for possible confounding effect of other explanatory variables as adjusted odds ratios (OR) with 95% confidence intervals (CI). Discrepancies in or between totals are due to rounding. Since the sample frame matched the Canadian census data from Statistics Canada, no additional survey weights were applied. We used RStudio Version 1.1.453 for analyses.

Ethics approval

The Angus Reid Forum obtained consent from all participants. The data without any personal identifiers are made available openly to bona-fide researchers. IRB approval for this study was obtained from Unity Health Toronto Research Ethics Board (REB# 20–107).

Results

Of the 4,240 respondents, 334 (or 7.9%) reported either themselves or at least one of the household members having COVID symptoms. Of these, 210 (5.0%) reported COVID symptoms only in themselves. The adjusted OR of the respondent having symptoms when at least one of the household members reported symptoms was 1.45 (95% CI 1.41–1.49); the OR was similar for at least one household member having symptoms if the respondent reported symptoms. In terms of testing for SARS-CoV-2, 126 (or 3.0%) reported some household testing or being scheduled for testing, and only 68 (or 1.6%) reported that they have been or are scheduled for testing. Details of the variation in COVID symptoms and SARS-CoV-2 testing in this sample across provinces have already been published [3].

Table 2 shows the adjusted OR of respondents or a member of the household, and respondents only having COVID symptoms after adjustment for other variables examined. We excluded 99 (or 2.3%) respondents who did not report on at least one of the variables. The proportion of respondents reporting COVID symptoms within the household decreased with age: 11.2% of those aged 18–45 years, 5.6% among those aged 46–65 years, and 3.1% among those aged 66 years and older. The lower prevalence at higher ages was similar among those reporting COVID symptoms only themselves. After controlling for gender, province, age, ethnicity, visible minority, and number of household members, older adults were significantly less likely to report having COVID symptoms themselves or within the household (age 46–65, OR = 0.55, 0.42–0.71; age 66+, OR = 0.30, 0.18–0.47). Those who reported themselves as a visible minority were significantly more likely to have COVID symptoms (12.9%) compared to those who did not (7.1%; adjusted OR = 1.55; 1.08–2.20). Similar results were found when we examined COVID symptoms only among respondents. The associations changed substantially between unadjusted and adjusted analyses, most notably for ethnicity, and somewhat for being a visible minority, suggesting that some residual confounding factors were present.

Table 2

Logistic regression models for respondents or a member of household, and respondents only having COVID symptoms.

Characteristics	Respondents or a member of household having symptoms			Respondents only having symptoms
	COVID symptoms present/absent		Adjusted odds ratios (95% CI)	COVID symptoms present/absent		Adjusted odds ratios (95% CI)
	N = 324/3817	%		N = 202/3939	%
Gender
Male	149/1840	7.5	Ref	85/1904	4.3	Ref
Female	175/1977	8.1	1.11 (0.89–1.40)	117/2036	5.4	1.30 (0.97–1.74)
Age group
18–45 years	218/1724	11.2	Ref	126/1816	6.5	Ref
46–65 years	84/1403	5.6	0.55 (0.42–0.71)	61/1426	4.1	0.61 (0.44–0.84)
66+ years	22/690	3.1	0.30 (0.18–0.47)	15/697	2.1	0.29 (0.16–0.50)
Education
Some college/university and higher	237/2874	8.4	Ref	150/2961	4.8	Ref
High school and under	87/943	7.6	1.25 (0.96–1.62)	52/978	5.1	1.16 (0.83–1.61)
Visible minority
No	256/3359	7.1	Ref	155/3460	4.3	Ref
Yes	68/458	12.9	1.55 (1.08–2.20)	47/479	8.9	2.08 (1.34–3.15)
Number of household members
Two people	108/1479	6.8	Ref	79/1507	5.0	Ref
Lived alone	29/626	4.4	0.69 (0.45–1.02)	29/626	4.5	1.01 (0.64–1.53)
Three people	77/704	9.9	1.17 (0.85–1.61)	45/736	5.8	0.86 (0.57–1.28)
Four or more people	110/1008	9.8	1.19 (0.89–1.59)	48/1070	4.3	0.72 (0.49–1.05)
Ethnicity
English and other European	252/3305	7.1	Ref	158/3399	4.4	Ref
Indigenous*	27/195	12.2	1.31 (0.83–2.01)	19/203	8.5	1.34 (0.76–2.24)
Others†	45/317	12.4	1.20 (0.79–1.80)	25/337	7.0	0.87 (0.50–1.47)
Province/region
Ontario	129/1448	8.2	Ref	83/1493	5.3	Ref
British Columbia	44/495	8.2	1.08 (0.77–1.51)	23/516	4.2	0.80 (0.51–1.24)
Quebec	65/922	6.6	0.93 (0.66–1.29)	42/945	4.2	0.85 (0.56–1.27)
Prairie provinces	63/674	8.5	1.09 (0.79–1.49)	39/697	5.2	0.98 (0.66–1.45)
Atlantic provinces	23/278	7.6	1.11 (0.68–1.76)	15/287	5.0	0.99 (0.53–1.74)

*Indigenous populations including First Nations, Inuit, or Métis.

†“Others” ethnicity includes Caribbean, Central or South American, African, Middle Eastern, Central Asian, Chinese, Filipino, South Asian, other Asian, and Oceania.

Bolded values indicate significance at 95% confidence interval. Adjustment was for the other variables in the table.

The number reporting COVID symptoms was 341 in unweighted analyses and 334 after weighing the sample to the Canadian census data, showing the sampling frame as robust.

Table 3 shows the adjusted OR of respondents or a member of the household being tested or scheduled for SARS-CoV-2 testing. The strongest predictor of testing was having COVID symptoms among members of the household, of whom about 16.5% were tested, compared to 2.1% among those without COVID symptoms among household members (OR = 6.63, 4.46–9.79). Testing rates fell with age, but not significantly so. Testing rates were 2.7% in English and other European ethnicity, and higher in those of indigenous ethnicity (7.2%; OR = 2.07; 1.13–3.64). However, the ORs fell notably (from 2.94 to 2.07) after adjustment for co-variates, suggesting residual confounding. Testing rates in Quebec were roughly double those in Ontario, the reference province (OR = 2.41; 1.49–3.96).

Table 3

Logistic regression models for respondent or a member of household having been tested for SARS-CoV-2.

Characteristics	Respondents or a member of household having been tested			Respondents only having been tested
	SARS-CoV-2 tested/not tested		Adjusted odds ratios (95% CI)	SARS-CoV-2 tested/not tested		Adjusted odds ratios (95% CI)
	N = 126/4015	%		N = 66/4075	%
Respondent and/or household member had COVID symptoms
No	80/3737	2.1	Ref	42/3775	1.1	Ref
Yes	46/278	16.5	6.63 (4.46–9.79)	24/300	7.5	6.63 (3.82–11.32)
Gender
Male	68/1921	3.5	Ref	34/1955	1.7	Ref
Female	58/2094	2.7	0.72 (0.51–1.03)	32/2120	1.5	0.85 (0.52–1.38)
Age group
18–45 years	84/1858	4.5	Ref	41/1900	2.1	Ref
46–65 years	32/1455	2.2	0.69 (0.45–1.05)	19/1468	1.3	0.75 (0.42–1.31)
66+ years	10/702	0.7	0.54 (0.25–1.05)	5/707	0.7	0.44 (0.14–1.08)
Education
Some college/university and higher	96/3015	3.1	Ref	52/3059	1.7	Ref
High school and under	29/1000	2.8	0.88 (0.56–1.35)	14/1016	1.3	0.74 (0.37–1.35)
Visible minority
No	96/3519	2.7	Ref	52/3563	1.4	Ref
Yes	30/496	5.7	0.83 (0.36–1.05)	14/512	2.7	0.54 (0.27–1.15)
Number of household members
Two people	38/1548	2.4	Ref	19/1567	1.2	Ref
Lived alone	13/642	2.0	0.83 (0.43–1.52)	13/642	2.0	1.77 (0.86–3.57)
Three people	28/754	3.6	1.18 (0.69–1.97)	18/764	2.3	1.28 (0.62–2.56)
Four or more people	47/1071	4.2	1.32 (0.84–2.09)	16/1102	1.4	0.93 (0.47–1.84)
Ethnicity
English and other European	95/3462	2.7	Ref	54/3503	1.5	Ref
Indigenous*	16/206	7.2	2.07 (1.13–3.64)	9/213	3.9	2.04 (0.89–4.28)
Others†	15/347	4.1	0.99 (0.49–1.89)	4/359	1.0	0.47 (0.13–1.32)
Province/region
Ontario	40/1537	2.5	Ref	22/1554	1.4	Ref
British Columbia	15/524	2.8	1.08 (0.59–1.93)	7/532	1.3	0.81 (0.34–1.81)
Quebec	47/940	4.8	2.41 (1.49–3.96)	26/961	2.6	1.98 (1.05–3.81)
Prairie provinces	19/717	2.6	1.13 (0.65–1.95)	7/730	1.0	0.74 (0.32–1.63)
Atlantic provinces	5/297	1.7	0.92 (0.34–2.14)	4/299	1.2	1.03 (0.29–2.87)

*Indigenous populations including First Nations, Inuit, or Métis.

†“Others” ethnicity includes Caribbean, Central or South American, African, Middle Eastern, Central Asian, Chinese, Filipino, South Asian, other Asian, and Oceania.

Bolded values indicate significance at 95% confidence interval. Adjustment was for the other variables in the table.

Discussion

A nationally representative survey of Canadians finds that about 8% of adults report that they or someone in their household reported symptoms suggestive of COVID in March 2020. Being a visible minority was associated with higher self-reported COVID symptoms. Self-reported symptoms were notably less common at older ages than in younger adults. Only 3% of Canadian adults reported that they or someone in the household had been tested for SARS-CoV-2. The main predictors of being tested were the presence of COVID symptoms, being of Indigenous identity, and living in Quebec. Testing rates were somewhat lower in older adults. There are surprisingly few national studies, and despite some limitations, this study represents the first to document self-reported symptoms in a reasonably representative sample.

COVID symptoms overlap with some other infections, notably seasonal influenza, which could have inflated the coronavirus rates in this survey. However, a study comparing the COVID symptom syndrome with other infections in the United States suggests that most are actually due to COVID [8]. We found possible COVID symptoms to be less prevalent and the levels of testing marginally less prevalent in older adults than other age groups, despite the certainty that the vast majority of COVID hospitalizations and deaths occur at older ages. However, a weakness of our sample is the lack of representation from nursing and long-term care residents, in whom more than three-quarters of all COVID deaths occur [1]. Approximately 0.3 million (out a total population of 38 million) Canadians are estimated to live in nursing homes/long-term care institutions [9]. This would represent less than 1% of the expected population in the survey. Such populations were under-represented in the survey. There may be additional reasons for the age-specific findings, however. Anecdotal reports suggest that older adults do not experience the symptoms used to define COVID infection in the poll, but may report vaguer symptoms such as dizziness and confusion [10]. Further surveys focused on syndromes that might occur in older adults are warranted. The testing results are broadly consistent with reports of the general levels of access to SARS-CoV-2 testing during the survey time period, including a higher level of testing in Quebec than in Ontario. However, testing results tend not to be representative of the population [3].

This syndromic survey provides some insights into the prevalence of actual SARS-CoV-2 in Canada. This time period of symptoms in March is consistent with testing data showing a peak exposure and incidence of COVID occurred in mid- to late April, presumably about 10–14 days in those adults who were tested because of their symptoms [1]. A Forum Research and Mainstreet Research reported an estimated prevalence of 5–8% in early-to-mid April in Ontario, which is consistent with our overall results for that province. However, they used a narrow range of symptoms from those we defined in our study [11].

In the UK, pilot results from the COVID-19 Infection Survey being carried out by the Office for National Statistics found that 0.25% of the community population in England above the age of 2, tested positive for the SARS-CoV-2 antigen in early-to-mid May 2020. Testing involved home self-tests of nasal swabs, and excluded those in hospitals, care homes, or other institutional settings [12]. The prevalence was lower than expected in the pilot, and larger studies are planned, along with antibody surveys. A nationally representative sero-epidemiological study is needed to establish the population distribution of cumulative SARS-CoV-2 infection, which would capture both symptomatic and asymptomatic cases. Such studies have now been conducted in England [13], Iceland [14], Brazil [15], and Spain [16]. We have begun such a study in Canada called Action to Beat Coronavirus/Action pour Battre le Coronavirus (Ab-C). The study protocol is provided in the (S2 Appendix). This study will determine the cumulative prevalence of SARS-CoV-2 infection during March-May 2020 in Canada through testing for IgG antibodies (using dual assays), paired with household questionnaire data on COVID experience. A second round of questionnaires and antibody testing four to six months later in the same individuals will provide information on ongoing transmission, changes in the immune status of the population, and the durability of the immune response. The Angus Reid Forum is partnering with the Centre for Global Health Research at Unity Health Toronto and the University of Toronto on this study. The expected sample frame is 14,000 individuals surveyed, of which we expect about 8,000 to agree to provide a blood sample.

The present analysis informs the design of antibody surveys. For example, since the strongest predictor of COVID testing was the presence of symptoms, a similar higher prevalence of antibodies might be expected among those reporting symptoms (who may be more likely to enroll in the survey). Thus, ensuring that the sample size is sufficiently large to examine the seroprevalence in those without symptoms is key. Similarly, while the current study did not examine geographic clustering of COVID symptoms, this might well be the case with actual SARS-CoV-2 infection. There have been calls for use of self-reported syndromic data to monitor the epidemic [17]. We believe, that these strategies should include also large and as diversely representative survey as possible. Older adults bear the brunt of COVID hospitalization and deaths. However, this population reported a lower prevalence of symptoms than younger adults. Thus, the Ab-C study will oversample the population age 60 or older, particularly to understand the possible role of asymptomatic infections at older ages. As the Ab-C study is not likely to capture the prevalence of infection among nursing home residents, ancillary studies are needed to quantify hazards among this important group.

Limitations

Self-reported symptoms are, by their nature, subject to limitations and misclassification. However, the trends over time, even with misclassification, are useful for understanding trends in the actual underlying prevalence of infection. This is because the “noise” of COVID symptoms should change little from one survey to the next, and provided there is large “signal” due to the COVID pandemic—certainly the case with this virus—reliable estimation of the trends of infection are possible. Similar methodological insights have arisen from HIV-1 testing in pregnant populations in various countries [18]. The biases in enrollment are also inherent in any polling, but the Angus Reid polling showed reasonably good consistency with the Canadian 2016 census. Moreover, the testing results did not appear to be biased greatly, and the more common testing reported in Quebec is consistent with public health reports. Another limitation of the study is that the survey questionnaire was not validated against serological results as none were available at the time of study design. However, subsequent studies comparing antibody with symptoms which we defined as suggestive of COVID in our study confirmed that our choice of symptoms was appropriate [19].

In conclusion, COVID surveillance using nationally representative surveys is essential, and ideally needs to be accompanied by antibody determination of infection. Particular attention must be paid to symptoms and testing levels in older adults.

COVID-19 questionnaire (Angus Reid Institute, wave 6).

(DOCX)

Click here for additional data file.

The Action to Beat Coronavirus/Action pour Battre le Coronavirus (Ab-C) study protocol.

(DOCX)

Click here for additional data file.

6 Jul 2020

PONE-D-20-16713

Determinants of self-reported symptoms and testing for COVID-19 in Canada using a nationally representative survey

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4. Please confirm whether a waiver of Ethics approval was obtained."

5. In your Methods section, please provide additional information about the participant recruitment method and the demographic details of your participants. Please ensure you have provided sufficient details to replicate the analyses such as: a) the recruitment date range (month and year), b) a description of any inclusion/exclusion criteria that were applied to participant recruitment, c) a table of relevant demographic details, d) a statement as to whether your sample can be considered representative of a larger population, e) a description of how participants were recruited, and f) descriptions of where participants were recruited and where the research took place. Furthermore, please provide more information on the survey used. in the methods section, please refer specifically to the questions used to assess variables; discuss how items (for example, the choice of COVID-19 symptoms) were originated; and  if you developed the questionnaire as part of this study and it is not under a copyright more restrictive than CC-BY, please include a copy, in both the original language and English, as Supporting Information. Moreover, please include more details on how the questionnaire was pre-tested, and whether it was validated. "

6. Please note that according to our submission guidelines (http://journals.plos.org/plosone/s/submission-guidelines), outmoded terms and potentially stigmatizing labels should be changed to more current, acceptable terminology. For example: “Caucasian” should be changed to “white” or “of [Western] European descent

7. Thank you for stating the following in the Financial Disclosure section:

"PJ received funding from the Canadian Institutes of Health Research (https://cihrirsc.

gc.ca/e/193.html; grant number: FDN 154277), and AR is funded by the Angus

Reid Institute (http://angusreid.org/). The Angus Reid Institute collected the data used

in this study and reviewed the manuscript."

We note that one or more of the authors are employed by a commercial company: "deltaDNA Biosciences, Inc.,".

a) Please provide an amended Funding Statement declaring this commercial affiliation, as well as a statement regarding the Role of Funders in your study. If the funding organization did not play a role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript and only provided financial support in the form of authors' salaries and/or research materials, please review your statements relating to the author contributions, and ensure you have specifically and accurately indicated the role(s) that these authors had in your study. You can update author roles in the Author Contributions section of the online submission form.

Please also include the following statement within your amended Funding Statement.

“The funder provided support in the form of salaries for authors [insert relevant initials], but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.”

If your commercial affiliation did play a role in your study, please state and explain this role within your updated Funding Statement.

b) Please also provide an updated Competing Interests Statement declaring this commercial affiliation along with any other relevant declarations relating to employment, consultancy, patents, products in development, or marketed products, etc.

Within your Competing Interests Statement, please confirm that this commercial affiliation does not alter your adherence to all PLOS ONE policies on sharing data and materials by including the following statement: "This does not alter our adherence to  PLOS ONE policies on sharing data and materials.” (as detailed online in our guide for authors ) . If this adherence statement is not accurate and  there are restrictions on sharing of data and/or materials, please state these. Please note that we cannot proceed with consideration of your article until this information has been declared.

Please include both an updated Funding Statement and Competing Interests Statement in your cover letter. We will change the online submission form on your behalf.

Please know it is PLOS ONE policy for corresponding authors to declare, on behalf of all authors, all potential competing interests for the purposes of transparency. PLOS defines a competing interest as anything that interferes with, or could reasonably be perceived as interfering with, the full and objective presentation, peer review, editorial decision-making, or publication of research or non-research articles submitted to one of the journals. Competing interests can be financial or non-financial, professional, or personal. Competing interests can arise in relationship to an organization or another person. Please follow this link to our website for more details on competing interests:

8. One of the noted authors is a group or consortium "Action to Beat Coronavirus in Canada/Action pour Battre le Coronavirus (Ab-C) Study Group". In addition to naming the author group, please list the individual authors and affiliations within this group in the acknowledgments section of your manuscript. Please also indicate clearly a lead author for this group along with a contact email address.

Additional Editor Comments (if provided):

Abstract to be structured as per PLOS ONE policy

Introduction should be more explicit, authors may wish to use Pubmed https://pubmed.ncbi.nlm.nih.gov/?term=Determinants+of+self-reported+symptoms+and+testing+for+COVID-19 and other literature search platform.

There is a need to describe the outcome variables and the independent variables including plausible covariates, this will assist reader to understand the variables of interests for determinant of self-reported symptoms and testing for COVID-19.

A bit of explanation on how data was managed to de-identify and assign unique identifier.

The statement of ethics should be very clear and the waiver reference number should be provided.

Include the statement for authors contribution

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: I Don't Know

Reviewer #2: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: REVIEWER COMMENT

The authors have presented a self-reported symptom and testing sampling of COVID-19 in Canada. Though a survey polling of this nature could come with some anecdotal exaggerations and biases, the study shows that the polling represents to a greater extent the Canadian census demographics.

MINOR COMMENTS

- The authors reported lower self-reported symptoms amongst the older age group, which they justified by the fact of differential presentation with dizziness and confusion, unlike the major listed symptoms for COVID.

- In addition, the authors reported “living in Quebec” (See line 133) as a determinant of “being tested”. It should be noted that Quebec has been the hardest hit province and this presupposes that the testing rates ought to be higher. If the authors want to make the assertion that “living in Quebec” is a determinant of “being tested”, they should try and run a regression with the testing rates and the number of reported COVID positive cases across the provinces when this data was collected. Otherwise, the authors may decide not to include that as a determinant.

Overall, the presentation and the flow are generally good for the readers to understand.

Reviewer #2: Title:

1.The author may consider revising the title to predictors of self-reported symptoms and testing for COVID 19 in Canada using a nationally representative survey. In view of the depth of the statistical analysis done.

Abstract:

1.The authors should consider including a sentence or two on COVID 19 as the opening narration of the abstract. This will bring to context the essence of the study.

Introduction:

1. The introduction will benefit from additional information on the subject matter (COVID 19) and not just the expression of what the study was all about.

Materials and Methods:

1.The authors should consider defining what constitutes the outcome variable (COVID 19) symptoms (present or absent) properly in the methodology as it was done in the abstract (COVID symptoms, defined as fever plus difficulty breathing/shortness of breath, dry cough so severe that it disrupts sleep, and/or loss of sense of smell). The abstract is expected to represent an excerpt of the content of the manuscript.

2.This manuscript will benefit from the details of how the survey weights was applied to the prevalence. Though a reference was provided but the cited document does not provide the needed clarity.

3.More information has to be provided by the authors on why IRB was not required for the study of this magnitude. It is also unclear what the statement "as per Unity Health Toronto Research Ethics Board" means. Was the ethics approval waived by unity Toronto Research Board? if so, reasons for such waiver have to be provided.

Results:

1. The information on the representativeness of the respondents by comparing the demographic characteristics with the Canadian population of 2019 will be more appropriate in the method as a standardization measure built into the study rather than having it in the results section.

2.Table 1; it is unclear what gender constitutes others in the absence of an appropriate footnote.

3. The authors should consider expunging the information on part of lines 133 to 115" Results using a narrower definition of COVID symptoms, namely having fever, difficulty breathing/shortness of breath, and severe dry cough were similar (data not shown) " as it is not adding any credence to the study.

4.Table 2; the authors may consider revising the expression used for categorizing the outcome variable (COVID symptoms) from positive/negative to present or absent. This revision may bring clarity to the fact that these symptoms were not tested for but rather self reported.

Discussion:

1.The discussion will be benefit from some revision by bringing in other similar available studies though it is a common knowledge that there is a paucity of such studies. Efforts should be made to get some of those studies available so as to enrich the discussion

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: Yes: Stanley Meribe

Reviewer #2: Yes: Tolulope Olumide Afolaranmi

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (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. Registration is free. 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 PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

16 Jul 2020

Revision to submission [PONE-D-20-16713]: Determinants of self-reported symptoms and testing for COVID-19 in Canada using a nationally representative survey

Comment 1- Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

Response 1- We have edited the manuscript to meet PLOS ONE’s style requirements.

Comment 2- We note that you have included the phrase “data not shown” in your manuscript. Unfortunately, this does not meet our data sharing requirements. PLOS does not permit references to inaccessible data. We require that authors provide all relevant data within the paper, Supporting Information files, or in an acceptable, public repository. Please add a citation to support this phrase or upload the data that corresponds with these findings to a stable repository (such as Figshare or Dryad) and provide and URLs, DOIs, or accession numbers that may be used to access these data. Or, if the data are not a core part of the research being presented in your study, we ask that you remove the phrase that refers to these data.

Response 2- We have removed those statements with the phrase “data not shown”, as these results were not a core part of the research being presented in our study.

Comment 3- Please clarify your Data availability statement. Please note that PLOS ONE criteria require that authors make all data underlying the findings described in their manuscript fully available without restriction at the time of publication. Authors should share any data specific to their analysis that they can legally distribute. For data that they cannot legally distribute, the authors must include in the Data Availability Statement all necessary contact information where an interested researcher would need to apply to gain access to the data; we do not allow an author to be the only point of contact for fielding requests for access to restricted data (for more information, please see https://journals.plos.org/plosone/s/data-availability).

We note that you have indicated that data from this study are available upon request. PLOS only allows data to be available upon request if there are legal or ethical restrictions on sharing data publicly. For information on unacceptable data access restrictions, please see http://journals.plos.org/plosone/s/data-availability#loc-unacceptable-data-access-restrictions.

Response 3- We have changed the Data availability statement (line 121-126).

In your revised cover letter, please address the following prompts:

a) If there are ethical or legal restrictions on sharing a de-identified data set, please explain them in detail (e.g., data contain potentially identifying or sensitive patient information) and who has imposed them (e.g., an ethics committee). Please also provide contact information for a data access committee, ethics committee, or other institutional body to which data requests may be sent.

b) If there are no restrictions, please upload the minimal anonymized data set necessary to replicate your study findings as either Supporting Information files or to a stable, public repository and provide us with the relevant URLs, DOIs, or accession numbers. Please see http://www.bmj.com/content/340/bmj.c181.long for guidelines on how to de-identify and prepare clinical data for publication. For a list of acceptable repositories, please see http://journals.plos.org/plosone/s/data-availability#loc-recommended-repositories.

We will update your Data Availability statement on your behalf to reflect the information you provide.

Response- We have revised the cover letter to reflect the legal and ownership restrictions on sharing de-identified dataset.

Comment 4- Please confirm whether a waiver of Ethics approval was obtained."

Response 4- IRB approval for this study was obtained from Unity Health Toronto Research Ethics Board (REB# 20-107).

Comment 5- In your Methods section, please provide additional information about the participant recruitment method and the demographic details of your participants. Please ensure you have provided sufficient details to replicate the analyses such as: a) the recruitment date range (month and year),

Response 5- We have provided the recruitment date range- April 1-5, 2020. Demographic details of the participants are given in the Results section in Table 1.

b) a description of any inclusion/exclusion criteria that were applied to participant recruitment,

Response- We have now provided the inclusion/exclusion criteria for participant recruitment (lines 62-63)

c) a table of relevant demographic details,

Response- We have included a table of relevant demographic details as Table 1.

d) a statement as to whether your sample can be considered representative of a larger population,

Response- We have included the statement: “The Angus Reid Institute (ARI) conducted an online survey from April 1-5, 2020, among a nationally representative randomized sample of 4,240 Canadian adults who are members of Angus Reid Forum, a national online sample of 50,000 Canadians used for political and other social polling”.

e) a description of how participants were recruited,

Response- The sampling frame is an existing Angus Reid Forum Panel (http://www.angusreidforum.com/), which is a national online sample of 50,000 adult Canadians used for political and other social polling (lines 60-61).

f) descriptions of where participants were recruited and where the research took place

Response- We have added this in lines 58-61, 87-90.

Furthermore, please provide more information on the survey used. In the methods section, please refer specifically to the questions used to assess variables;

Response- We have now added this in lines 95-106, 107-110.

Discuss how items (for example, the choice of COVID-19 symptoms) were originated;

Response- We have now added this in lines 83-84.

and if you developed the questionnaire as part of this study and it is not under a copyright more restrictive than CC-BY, please include a copy, in both the original language and English, as Supporting Information.

Response- We have now added the questionnaire as Supporting Information (S1 Appendix).

Moreover, please include more details on how the questionnaire was pre-tested, and whether it was validated. "

Response-The questionnaire was pre-tested as per standard polling procedures in about 60 people. Validation of symptoms was not possible at the time against antibody status but is planned in the main Ab-C study. We have added a line of pre-testing (lines 85-86).

Comment 6- Please note that according to our submission guidelines (http://journals.plos.org/plosone/s/submission-guidelines), outmoded terms and potentially stigmatizing labels should be changed to more current, acceptable terminology. For example: “Caucasian” should be changed to “white” or “of [Western] European descent.

Response 6- We have changed our terminologies from “Caucasian” to “white” and from “indigenous people” to “those of self-identified indigenous ethnicity”.

Comment 7- Thank you for stating the following in the Financial Disclosure section: "PJ received funding from the Canadian Institutes of Health Research (https://cihrirsc.gc.ca/e/193.html; grant number: FDN 154277), and AR is funded by the Angus Reid Institute (http://angusreid.org/). The Angus Reid Institute collected the data used in this study and reviewed the manuscript." We note that one or more of the authors are employed by a commercial company: "deltaDNA Biosciences, Inc.,".

a) Please provide an amended Funding Statement declaring this commercial affiliation, as well as a statement regarding the Role of Funders in your study. If the funding organization did not play a role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript and only provided financial support in the form of authors' salaries and/or research materials, please review your statements relating to the author contributions, and ensure you have specifically and accurately indicated the role(s) that these authors had in your study. You can update author roles in the Author Contributions section of the online submission form.

Please also include the following statement within your amended Funding Statement.

“The funder provided support in the form of salaries for authors [insert relevant initials], but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.”

If your commercial affiliation did play a role in your study, please state and explain this role within your updated Funding Statement.

Response 7a-“We have updated the funders. The commercial affiliation is only that for CB and no funding was involved. We have added the statement: “The funders provided support in the form of salaries for authors [DCW, HG], but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.”

Comment 7b- Please also provide an updated Competing Interests Statement declaring this commercial affiliation along with any other relevant declarations relating to employment, consultancy, patents, products in development, or marketed products, etc.

Within your Competing Interests Statement, please confirm that this commercial affiliation does not alter your adherence to all PLOS ONE policies on sharing data and materials by including the following statement: "This does not alter our adherence to PLOS ONE policies on sharing data and materials.” (as detailed online in our guide for authors http://journals.plos.org/plosone/s/competing-interests) . If this adherence statement is not accurate and there are restrictions on sharing of data and/or materials, please state these. Please note that we cannot proceed with consideration of your article until this information has been declared.

Please include both an updated Funding Statement and Competing Interests Statement in your cover letter. We will change the online submission form on your behalf.

Please know it is PLOS ONE policy for corresponding authors to declare, on behalf of all authors, all potential competing interests for the purposes of transparency. PLOS defines a competing interest as anything that interferes with, or could reasonably be perceived as interfering with, the full and objective presentation, peer review, editorial decision-making, or publication of research or non-research articles submitted to one of the journals. Competing interests can be financial or non-financial, professional, or personal. Competing interests can arise in relationship to an organization or another person. Please follow this link to our website for more details on competing interests: http://journals.plos.org/plosone/s/competing-interests

Response 7b- We declare no competing interests.

Comment 8- One of the noted authors is a group or consortium "Action to Beat Coronavirus in Canada/Action pour Battre le Coronavirus (Ab-C) Study Group". In addition to naming the author group, please list the individual authors and affiliations within this group in the acknowledgments section of your manuscript. Please also indicate clearly a lead author for this group along with a contact email address.

Response 8- We have added the list of individual authors and affiliations within the group, "Action to Beat Coronavirus in Canada/Action pour Battre le Coronavirus (Ab-C) Study Group" in the Acknowledgement section, along with the lead author and contact email address.

Additional Editor Comments

Comment 1- Abstract to be structured as per PLOS ONE policy.

Response 1- We have structured the abstract as per PLOS ONE policy.

Comment 2-Introduction should be more explicit, authors may wish to use pubmed https://pubmed.ncbi.nlm.nih.gov/?term=Determinants+of+self-reported+symptoms+and+testing+for+COVID-19 and other literature search platform.

Response 2- We have revised the Introduction to be more explicit.

Comment 3- There is a need to describe the outcome variables and the independent variables including plausible covariates, this will assist reader to understand the variables of interests for determinant of self-reported symptoms and testing for COVID-19.

Response 3- We have now provided a description of the outcome and independent variables (lines 94-110).

Comment 4- A bit of explanation on how data was managed to de-identify and assign unique identifier.

Response 4- We have now added details on how data was managed to de-identify and assign unique identifier (lines 88-90).

Comment 5- The statement of ethics should be very clear and the waiver reference number should be provided.

Response 5- We have now added the research ethics statement and the ethics approval number (line 118-119).

Comment 6- Include the statement for authors contribution.

Response 6- We have now added the statement for authors’ contribution in the title page.

Reviewers’ comments

Reviewer #1: REVIEWER COMMENT

The authors have presented a self-reported symptom and testing sampling of COVID-19 in Canada. Though a survey polling of this nature could come with some anecdotal exaggerations and biases, the study shows that the polling represents to a greater extent the Canadian census demographics.

MINOR COMMENTS

- The authors reported lower self-reported symptoms amongst the older age group, which they justified by the fact of differential presentation with dizziness and confusion, unlike the major listed symptoms for COVID.

- In addition, the authors reported “living in Quebec” (See line 133) as a determinant of “being tested”. It should be noted that Quebec has been the hardest hit province and this presupposes that the testing rates ought to be higher. If the authors want to make the assertion that “living in Quebec” is a determinant of “being tested”, they should try and run a regression with the testing rates and the number of reported COVID positive cases across the provinces when this data was collected. Otherwise, the authors may decide not to include that as a determinant.

Response- We mention that testing rates are higher in Quebec in the discussion but do not believe it is appropriate to run a regression of testing data (which unlike this survey) are not representative versus symptom data.

Overall, the presentation and the flow are generally good for the readers to understand.

Reviewer #2: Title:

1.The author may consider revising the title to predictors of self-reported symptoms and testing for COVID 19 in Canada using a nationally representative survey. In view of the depth of the statistical analysis done.

Response 1- We have revised the title to predictors of self-reported symptoms and testing for COVID-19 in Canada using a nationally representative survey.

Abstract:

1.The authors should consider including a sentence or two on COVID 19 as the opening narration of the abstract. This will bring to context the essence of the study.

Response 1- We have now included a sentence on estimating the prevalence of COVID at the beginning of the abstract (lines 24-26).

Introduction:

1. The introduction will benefit from additional information on the subject matter (COVID 19) and not just the expression of what the study was all about.

Response 1- We have now added more information on COVID in the Introduction (lines 41-42).

Materials and Methods:

1.The authors should consider defining what constitutes the outcome variable (COVID 19) symptoms (present or absent) properly in the methodology as it was done in the abstract (COVID symptoms, defined as fever plus difficulty breathing/shortness of breath, dry cough so severe that it disrupts sleep, and/or loss of sense of smell). The abstract is expected to represent an excerpt of the content of the manuscript.

Response 1- We have now added the definition of COVID symptoms in the Methods section (lines 75-78).

2.This manuscript will benefit from the details of how the survey weights was applied to the prevalence. Though a reference was provided but the cited document does not provide the needed clarity.

Response 2- We have now added a statement of how weightings were applied to prevalence (lines 112-113).

3.More information has to be provided by the authors on why IRB was not required for the study of this magnitude. It is also unclear what the statement "as per Unity Health Toronto Research Ethics Board" means. Was the ethics approval waived by unity Toronto Research Board? if so, reasons for such waiver have to be provided.

Response 3- We have obtained IRB approval from Unity Health Toronto (lines 118-119)

Results:

1. The information on the representativeness of the respondents by comparing the demographic characteristics with the Canadian population of 2019 will be more appropriate in the method as a standardization measure built into the study rather than having it in the results section.

Response 1- We have now moved this to the Methods section.

2.Table 1; it is unclear what gender constitutes others in the absence of an appropriate footnote.

Response 2- We have now included a footnote to clarify what “other” gender constitutes.

3. The authors should consider expunging the information on part of lines 133 to 115" Results using a narrower definition of COVID symptoms, namely having fever, difficulty breathing/shortness of breath, and severe dry cough were similar (data not shown) " as it is not adding any credence to the study.

Response 3- We have now removed the statement.

4.Table 2; the authors may consider revising the expression used for categorizing the outcome variable (COVID symptoms) from positive/negative to present or absent. This revision may bring clarity to the fact that these symptoms were not tested for but rather self reported.

Response 4- We have now changed the expression from “positive/negative” to “present/absent”.

Discussion:

1.The discussion will be benefit from some revision by bringing in other similar available studies though it is a common knowledge that there is a paucity of such studies. Efforts should be made to get some of those studies available so as to enrich the discussion.

Response 1- We have made the point about such studies being required in the discussion and cited a recent NEJM paper.

Submitted filename: Response to reviewers.docx

Click here for additional data file.

21 Sep 2020

PONE-D-20-16713R1

Predictors of self-reported symptoms and testing for COVID-19 in Canada using a nationally representative survey

PLOS ONE

Dear Dr. Jha,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Reviewer 2 still has some minor clarification issues that should not be difficult to address.

Please submit your revised manuscript by Nov 05 2020 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

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A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

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If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

We look forward to receiving your revised manuscript.

Kind regards,

Gabriel A. Picone

Academic Editor

PLOS ONE

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: I do not have any further comments to the Authors. My earlier comments have been responded to and clarified.

Reviewer #2: The authors have painstakingly revised the manuscript in line with the review comments. However, the following revision will be required in order to make the manuscript publication worthy.

1. It is still unclear how the weighting of the sample size was done. This will require the authors to provide more details so as to bring clarity to it.

2. It is important for the authors to provide information on the source of the data collection instrument; was it adopted, adapted or developed for this study? Also, the method(s) of validating or assessing the reliability of the tool may be required. The statement on line 79 is unclear, which sampling frame were the authors referring to? The pretesting should not have been done among the same subjects who participated in the survey because it would have pre-empted them "The survey instrument was pre-tested in 60 individuals within the sampling frame."

3. It will also be good if the authors provide some sentence on the measures of used e.g. crude and adjusted odds ratio and the 95% confidence interval and rationale for using them in the data analysis section.

4. There is the need to provide footnotes for other ethnicity in tables 2 and 3.

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Reviewer #1: Yes: Stanley Meribe, MD, PhD

Reviewer #2: Yes: Tolulope Olumide Afolaranmi

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Submitted filename: Review comments for PLoS One manuscript.docx

Click here for additional data file.

22 Sep 2020

Comment 1- The authors have painstakingly revised the manuscript in line with the review comments. However, the following revision will be required in order to make the manuscript publication worthy.

It is still unclear how the weighting of the sample size was done. This will require the authors to provide more details so as to bring clarity to it.

Response- We have now added a line stating that “The sample frame was established to match the Canadian census data from Statistics Canada.” (lines 58-59) under the Study design section. We have now also mentioned that “Since the sample frame matched the Canadian census data from Statistics Canada, no additional survey weight was applied.” (lines 109-110).

Comment 2- It is important for the authors to provide information on the source of the data collection instrument; was it adopted, adapted or developed for this study? Also, the method(s) of validating or assessing the reliability of the tool may be required. The statement on line 79 is unclear, which sampling frame were the authors referring to? The pretesting should not have been done among the same subjects who participated in the survey because it would have pre-empted them "The survey instrument was pre-tested in 60 individuals within the sampling frame."

Response- We have now added a line on the source of the data collection instrument stating that the questionnaire used for this study was developed based on expert opinion (line 80). We have clarified that the 60 people were tested prior to the main survey (our apologies for the earlier error) (line 83). The data collection instrument (questionnaire) was not “validated” as at the time of survey, there were no reliable seroepidemiological studies that related infection with symptoms (line 235-237). However, subsequent studies comparing antibody with symptoms which we defined as suggestive of COVID in our study confirmed that our choice of symptoms was appropriate. We have also mentioned this in the Limitations section (line 237-239).

Comment 3- It will also be good if the authors provide some sentence on the measures of used e.g. crude and adjusted odds ratio and the 95% confidence interval and rationale for using them in the Analysis section.

Response- We have now provided a sentence on the measure of outcome used (adjusted odds ratio and 95% confidence interval) and the rationale for using them in the Data analysis section (lines 106-108).

Comment 4- There is the need to provide footnotes for other ethnicity in tables 2 and 3.

Response- We have now included footnotes for “Others” ethnicity in tables 1, 2, and 3 listing the list of included ethnicities.

Submitted filename: Response to Reviewers.docx

Click here for additional data file.

5 Oct 2020

Predictors of self-reported symptoms and testing for COVID-19 in Canada using a nationally representative survey

PONE-D-20-16713R2

Dear Dr. Jha,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Gabriel A. Picone

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: All comments have been addressed

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Reviewer #2: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: Yes

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Reviewer #2: Yes

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PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #2: Yes

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Reviewer #2: The authors have revised the manuscript in line with all the review comments. I am positive that this manuscript is publication worthy and will be of interest to readers in the scientific community.

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Reviewer #2: Yes: Tolulope Olumide Afolaranmi

16 Oct 2020

PONE-D-20-16713R2

Predictors of self-reported symptoms and testing for COVID-19 in Canada using a nationally representative survey

Dear Dr. Jha:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

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