Abstract
BackgroundNursing home (NH) residents have been severely affected during the COVID-19 pandemic because of their age and underlying comorbidities. Infection and outbreaks in NHs are most likely triggered by infected workers. Screening for asymptomatic NH workers can prevent risky contact and viral transmission to the residents. This study examined the effect of the BNT162b2 mRNA COVID‑19 (Comirnaty®; BioNTech and Pfizer) vaccination on the saliva excretion of SARS-CoV-2 among NH workers, through weekly saliva RT-qPCR testing.MethodsA 2-month cohort study was conducted among 99 NHs in the Walloon region (Belgium), at the start of February 2021. Three groups of workers, i.e., non-vaccinated (n = 1618), one-dosed vaccinated (n = 1454), and two-dosed vaccinated (n = 2379) of BNT162b2 mRNA COVID‑19 vaccine, were followed-up weekly. Their saliva samples were used to monitor the shedding of SARS-CoV-2. All positive samples were sequenced and genotyped to identify the circulating wild-type virus or variants of concern.ResultsThe protection fraction against the excretion of the SARS-CoV-2 in the saliva samples of the workers after the second dose is estimated at 0.90 (95% CI: 0.18; 0.99) at 1 week and 0.83 (95% CI: 0.54; 0.95) at 8 weeks. We observe more circulating SARS-CoV-2 and a greater variability of viral loads in the unvaccinated group compared to those of the vaccinated group.ConclusionsThis field cohort study advances our knowledge of the efficacy of the mRNA BNT162b2 COVID-19 vaccine on the viral shedding in the saliva specimens of vaccinated NH workers, contributing to better decision-making in public health interventions and management.
Highlights
Nursing home (NH) residents have been severely affected during the COVID-19 pandemic because of their age and underlying comorbidities
Based on specific governmental measures implemented in Belgium during the COVID-19 pandemic, five periods of interest were identified: the first wave, the inter-wave period (June 22 until August 30, 2020), the second wave, the third wave directly after the second, and the fourth wave starting at 4th October 202115
The number of active NHs in the Walloon region of Belgium was estimated at 57221. Based on this sampling frame, no significant difference was observed between participating (N = 99) and non-participating (N = 472) NHs in the cohort study according to province and NH worker population size taking into account the possible interaction between the two parameters (Logistic regression; p value > 0.10) (Fig. 2)
Summary
Background Nursing home (NH) residents have been severely affected during the COVID-19 pandemic because of their age and underlying comorbidities. Infection and outbreaks in NHs are most likely triggered by infected workers. Screening for asymptomatic NH workers can prevent risky contact and viral transmission to the residents. This study examined the effect of the BNT162b2 mRNA COVID‐19 (Comirnaty®; BioNTech and Pfizer) vaccination on the saliva excretion of SARS-CoV-2 among NH workers, through weekly saliva RT-qPCR testing. I.e., non-vaccinated (n = 1618), one-dosed vaccinated (n = 1454), and two-dosed vaccinated (n = 2379) of BNT162b2 mRNA COVID‐19 vaccine, were followed-up weekly. Their saliva samples were used to monitor the shedding of SARS-CoV-2. All positive samples were sequenced and genotyped to identify the circulating wild-type virus or variants of concern
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