Study population and setting
This prospective study followed 31 residents and 59 staff members at a nursing home unit in Jura, France. Residents were eligible to receive the BNT162b2 (Pfizer) mRNA vaccine starting in January 2021, and 26/31 (83.9%) were fully vaccinated prior to the start of the study. Among staff members, 16/59 (32.2%) were vaccinated. Residents and staff were followed from March 8, 2021, when a resident was diagnosed with the Beta (501Y.V2) SARS-CoV-2 variant until March 29, 2021. All residents and staff were tested at baseline and every seven days, or with the onset of symptoms, with nasopharyngeal swabs until there were no further positive test results. Some positive RT-PCR tests were sequenced with next-generation sequencing. Vaccinated individuals who tested positive for SARS-CoV-2 were also tested for nucleoprotein and receptor-binding domain spike protein antibodies with enzyme immunoassay.
Summary of Main Findings
The included residents had a mean age of 87 years (standard deviation 8.2 years) and were 64.5% female. Between the first Beta variant diagnosis on March 8, 2021 and March 29, 2021, there were 18 total residents and 11 staff members with evidence of SARS-CoV-2; the last positive test occurred on March 15, 2021. Of 10 samples sequenced from residents, all were positive for the Beta variant. Among the 26 vaccinated residents, 13 (50%) were infected, whereas all 5 (100%) non-vaccinated residents were infected. The BNT162b2 vaccine was therefore 50% (95% CI: 34-73%) efficacious against SARS-CoV-2 infection among residents. Among the vaccinated residents, who had various levels of anti-spike antibodies at diagnosis that did not correlate with disease severity, two (15.4%) had asymptomatic disease, nine (69.2%) developed mild to moderate symptoms, and two (15.4%) died after developing severe disease. Among unvaccinated residents, four (80%) developed severe disease and one (20%) died. One (5.2%) vaccinated staff member versus ten (25%) unvaccinated staff members were infected, none of whom developed severe disease.
This study prospectively followed the transmission of the Beta SARS-CoV-2 variant through a presumably closed population that included vaccinated and unvaccinated nursing home residents and staff, a highly vulnerable population to negative COVID-19 outcomes.
This study is very small, making it difficult to generalize their findings to a broader population. The study also presumed a closed population, though samples from only ten of the 29 infected residents and staff members were sequenced to confirm infection with the Beta variant. It is unclear how the original resident was infected with SARS-CoV-2 and whether subsequent infections were from the original resident with the Beta variant or from exposure to contacts outside the nursing home, possibly with another variant in the untested individuals. If, for example, staff members brought a different community-acquired SARS-CoV-2 variant strain into the nursing home, that would make it more difficult to interpret the results of this study as with regard to the BNT162b2 vaccine’s efficacy against infection with the Beta variant of SARS-CoV-2.
This study suggests that BNT162b2 vaccination substantially decreased but did not eliminate Beta SARS-CoV-2 variant infectivity and severity in a nursing home population.
This review was posted on: 27 June 2021