The original monovalent (single-strain) COVID-19 mRNA booster lowered combined COVID-19 hospitalization or death by 80% and 64% in two multistate nursing home systems during a period dominated by the Delta and Omicron variants, suggests a study published yesterday in JAMA Network Open.
Researchers from the Veterans Administration Medical Center in Province, Rhode Island; Brown University; and Genesis HealthCare in Kennett Square, Pennsylvania, analyzed electronic health records to estimate the booster-related reduction in COVID-19 infections, hospitalizations, and deaths among 10,949 residents of 202 Genesis HealthCare nursing homes (system 1) and 4,321 residents of 128 Veterans Health Administration nursing homes (system 2).
The residents had completed a primary COVID-19 vaccine series and were eligible for a Pfizer/BioNTech booster dose from Sep 22 to Nov 30, 2021, with 12-week follow-up until Mar 8, 2022.
38% and 58% decline in hospitalizations
System 1 had 8,332 booster recipients who were 63.9% women and 80.2% White and 10,886 unboosted residents who were 63.1% women and 79.5% White. Median age was 78 years. System 2 had 3,289 booster recipients who were 96.0% men and 59.3% White and 4,317 unboosted residents who were 96.2% men and 56.4% White. Median age was 74 years.
Booster vaccination was tied to declines in COVID-19 infections of 37.7% in system 1 and 57.7% in system 2. Hospitalizations fell by 74.4% in system 1 and 64.1% in system 2. Estimated vaccine effectiveness (VE) for COVID-related death was 87.9% in system 1. While system 2 saw a reduction in death of 46.6%, it wasn't statistically significant.
Compared with booster recipients in system 2, those in system 1 had higher rates of COVID-19 infection (100.1 infections per 1,000 residents vs 72.5/1,000) and death (1.4 deaths/1,000 residents vs 1.3/1,000) but lower rates of hospitalization (3.9/1,000 vs 31.2/1,000).
Administration of vaccine boosters to nursing home residents may have an important role in preventing severe COVID-19 outcomes.
Forty-five residents died of COVID-19 in system 1, and 18 died in system 2. Booster recipients in system 1 saw an 80.3% reduction in combined hospitalization or death, and those in system 2 had a 63.8% decline.
VE differed in the two systems mostly in terms of hospitalization rates, with the need for booster vaccination of an estimated 47 residents in system 1 and 18 in system 2 to prevent 1 COVID-19 hospitalization or death.
Key role for boosters
The study authors said that nursing homes are an ideal setting in which to estimate VE because of residential stability, systematic documentation of vaccination, and frequent COVID-19 testing.
"The present work evaluated VE by using an emulated trial design, which allowed us to include unboosted participants with characteristics comparable with those of boosted participants who differed primarily by the date on which they received a SARS-CoV-2 vaccine rather than by indication, baseline covariates, or exposure risk to circulating strains," they wrote.
The results, the researchers said, suggest that administration of vaccine boosters to nursing home residents may have an important role in preventing severe COVID-19 outcomes. "Additional clinical evidence of booster effectiveness may support efforts to increase booster distribution for this vulnerable population," they wrote.