The impact of visitor restrictions on health care-associated respiratory viral infections during the COVID-19 pandemic: Experience of a tertiary hospital in Singapore.

To the Editor:

We read with interest the recent article by Weiner et al that described hospital visitation policies during the coronavirus disease 2019 (COVID-19) pandemic, and called for epidemiological evidence to support and inform the imposition of visitor restrictions. Indeed, the imposition of visitor restrictions has been introduced in various healthcare settings to mitigate transmission of SARS-CoV-2; , however, as such measures were typically imposed as part of a bundle of other infection-prevention measures, the actual contribution of visitor restrictions in minimizing health care-associated transmission of respiratory-viral-infections (RVIs) is unclear. Furthermore, evidence is emerging that restricting access to family caregivers and visitors poses risks of social isolation, psychological distress, and delayed recovery, which has to be weighed against potential benefits associated with preventing health care-associated RVIs (HA-RVI).

In Singapore, a Southeast Asian city-state, various infection-prevention measures were implemented soon after the first reported case of COVID-19 in end-January 2020. From February 2020 onward, a COVID-19 containment strategy was implemented across the largest health care campus in Singapore, comprising the Singapore General Hospital (SGH), the largest acute tertiary hospital in Singapore (1735 beds); a 545-bed community hospital as well as four subspecialty centers in cardiology, neurology, ophthalmology, and oncology, all located on a single site (Fig 1 a). Our institution's campus-wide approach involved improved segregation of patients with respiratory symptoms, universal masking of staff, patients and visitors, point-of-entry temperature screening for all staff and visitors, as well as visitor limitations/visitor restrictions. All visitors underwent mandatory screening upon entry; visitors with fever, respiratory symptoms or significant travel/epidemiological history would be denied entry (Fig 1b). Prior to the pandemic, a visitor limit of 4 visitors was in-place; from February 2020 onward, only 1 visitor was allowed. In April-May 2020, visitor restrictions were instituted and no visitors were allowed. From June 2020 onward, hospitalized inpatients were allowed a single visitor; finally, from August 2020 onward, visitor limits were relaxed to 2 visitors (Fig 1c). The combined infection-prevention bundle was remarkably successful in mitigating health care-associated transmission of SARS-CoV-2, with no patient/visitor-HCW transmission. As an unintended positive consequence, a substantial decrease in HA-RVI was detected soon after introduction of the infection-prevention bundle, though simultaneous introduction made it difficult to ascertain the specific contribution of visitor restriction. However, given that visitor restrictions were relaxed progressively while all other infection-prevention measures were maintained, it was possible to evaluate if the relaxation of visitor restrictions coincided with a subsequent rebound in HA-RVI.

Fig 1

Campus wide visitor screening and visitor limitations/restrictions, as well as trends in health care-associated respiratory viral infections (HA-RVI) from January 2018 to September 2020 across a large health care system in Singapore. (A) Trends in healthcare-associated respiratory viral infections across all inpatient wards of a large healthcare campus in Singapore, from January 2018 to September 2020. (B) Visitor screening at all campus-wide entrances during COVID-19 pandemic. (C) Visitor policies introduced during COVID-19 pandemic and timeline of introduction/rollback.

Over an 8-month study period from February 2020 to September 2020, all symptomatic inpatients campus-wide were tested for COVID-19 and 16 common RVIs, including influenza, via multiplex PCR. Cases of RVI were categorized as HA-RVI if the RVI was identified beyond the maximum incubation period from the time of admission. Comparisons of HA-RVI rates during the pandemic period were compared with the prepandemic period (January 2018-January 2020) using the incidence-rate-ratio (IRR) method, with the null hypothesis being that the incidence of HA-RVI would be proportional to the number of inpatient days at-risk for each period. Trends in HA-RVI were then correlated against the sequential imposition and relaxation of visitor restrictions/limits. The institutional review board of SGH approved the study and waived informed consent.

Prior to the COVID-19 outbreak, the campus-wide cumulative incidence of HA-RVI was 9.69 cases per-10,000 patient-days (989 cases; 1,020,463 patient-days). After visitor limitations (single-visitor policy) were introduced together with other infection prevention measures in February 2020, the cumulative incidence of PCR-proven HA-RVI fell to 2.23 cases per-10,000 patient-days (15 cases; 67,335 patient-days), a statistically significant decrease (IRR = 0.23, 95% confidence interval [CI] = 0.13-0.38, P < .001) (Fig 1a). From April to May 2020, after the imposition of visitor restrictions (no-visitors policy), the cumulative incidence of HA-RVI fell further to 0.66 cases per-10,000 patient-days (5 cases; 75,203 patient-days; IRR = 0.30, 95% CI = 0.08-0.86, P = .013). From June to July 2020, after the rollback of visitor restrictions (single-visitor policy), the cumulative incidence of HA-RVI remained low, at 0.24 cases per-10,000 patient-days (2 cases; 81,866 patient-days); there was no statistically significant difference in HA-RVI compared with the preceding 2 months when visitor restrictions were enforced (IRR = 0.36, 95% CI = 0.03-2.24, P = .212). Finally, from August to September 2020, after the further relaxation of visitor limitations (two-visitor policy), the cumulative incidence of HA-RVI remained at 0.12 cases per-10,000 patient-days (1 case; 80,602 patient-days); further relaxation of visitor limitations did not coincide with a significant increase in HA-RVI (IRR = 0.57, 95% CI = 0.01-9.76, P = .573). Over the study period, despite managing ≥1,600 cases of COVID-19, only 1 case of potential health care-associated transmission was detected.

The key finding of this study is that while visitor restrictions introduced as part of an infection-prevention bundle initially coincided with a significant and substantial drop in health care-associated transmission of common RVIs across a large health care campus, the subsequent rollback of visitor restrictions and visitor limitations was not associated with a subsequent rebound in HA-RVI. Visitor management complements other infection prevention efforts and needs to be calibrated carefully taking into consideration patients' psychological well-being and prevention of infection transmission.