COVID-19 mRNA vaccines show sustained effectiveness against hospitalization in U.S. veterans

An observational study conducted at five Veterans Affairs Medical Centers in the United States evaluated the effectiveness of COVID-19 mRNA vaccines against COVID-19-associated hospitalization among U.S. veterans. The study period spanned from February 1 to August 6, 2021, which included the spread of the Delta variant. The primary finding was that COVID-19 mRNA vaccine effectiveness 'remains high,' though the study did not report specific effect sizes, absolute numbers, confidence intervals, or p-values.

No safety, tolerability, or adverse event data were reported for this analysis. The study did not specify a comparator group, and the sample size was not reported.

Key limitations include the observational study design, which can only show association, not causation. The lack of reported quantitative data on vaccine effectiveness, such as hazard ratios or vaccine efficacy percentages, limits the precision of the findings. The population was restricted to U.S. veterans receiving care at VA facilities, which may not be fully generalizable to other populations.

For practice, this evidence suggests a continued association between mRNA vaccination and protection against severe COVID-19 outcomes in this specific veteran population during the observed period. However, clinicians should interpret these findings with appropriate caution due to the observational nature of the evidence and the absence of detailed numerical results.