ABSTRACT
BackgroundA SARS-CoV-2 vaccine booster dose has been recommended for all nursing home residents. However, we lack effectiveness data on boosters preventing infection, death and hospitalization in this frail population. MethodsWe emulated nested target trials in two large nursing home systems in parallel to evaluate the effectiveness of a SARS-CoV-2 mRNA vaccine booster at preventing infection, hospitalization, or death. Residents who completed a 2-dose series of the mRNA vaccine and were eligible for a booster were included in from September 22, 2021 to November 5, 2021. Outcomes were measured through December 18, 2021, including test-confirmed SARS-CoV-2 infection, hospitalization, or death. The vaccine effectiveness at day 42 was estimated with a Kaplan-Meier estimator, both unadjusted and weighted with the inverse probability of treatment. ResultsThe two NH systems were large and multi-state, System 1 included 200 NH (8,538 control and 5,721 boosted residents) and System 2 included 127 NHs (4,100 control and 2,291 boosted residents). Booster vaccination reduced infections by 50.4% (95% Confidence Interval [CI]: 29.4%, 64.7%) SARS-CoV-2 infections in System 1 and 58.2% (32.3%, 77.8%) in System 2. Boosted residents in System 1 also had a 97.3% (86.9%, 100.0%) reduction in SARS-CoV-2 associated death, but too few events for comparison in System 2. ConclusionsDuring a Delta predominant period, SARS-CoV-2 booster vaccination significantly reduced infection in two U.S. nursing home systems. In the larger System 1 a 97% reduction in SARS-CoV-2 related death was also observed. These findings strongly support administration of vaccine boosters to nursing home residents.
ABSTRACT
Nursing home (NH) residents have experienced significant morbidity and mortality to SARS-CoV-2 throughout the pandemic. Vaccines initially curbed NH resident morbidity and mortality, but antibody levels and protection have declined with time since vaccination, prompting introduction of booster vaccination. This study assesses humoral immune response to booster vaccination in 85 NH residents and 44 health care workers (HCW) that we have followed longitudinally since initial SARS-CoV-2 BNT162b2 mRNA vaccination. The findings reveal that booster vaccination significantly increased anti-spike, anti-receptor binding domain, and neutralization titers above the pre-booster levels in almost all NH residents and HCW to significantly higher levels than shortly after the completion of the initial vaccine series. These data support the CDC recommendation to offer vaccine boosters to HCWs and NH residents on an immunological basis. Notably, even the older, more frail and more multi-morbid NH residents have sizable antibody increases with boosting.