Temporal patterns of all-cause mortality among U.S. nursing home residents across COVID-19 vaccination strata, May 2022-June 2023

Background: Most research on COVID 19 vaccine safety and efficacy has focused on working age adults and disease specific outcomes, with limited evidence concerning impacts on overall mortality in the elderly. This clinical epidemiological study examines all cause mortality in U.S. long term care facilities, addressing a critical gap in understanding the associations between COVID-19 vaccination and total mortality among frail residents. Methods: We analyzed publicly available facility level Medicare data from 15,022 nursing homes, reported weekly to the U.S. Centers for Disease Control from May 2022 to June 2023, including residents' all cause deaths and SARS CoV 2 test results stratified by vaccination status. We modeled mortality relative to COVID 19 positive case counts using mixed Poisson regression adjusted for time invariant and -varying confounders. Lagged and reverse lagged models examined and validated temporal directionality. Results: All cause mortality rates rose during weeks with more COVID 19 positive residents. Relative to unvaccinated residents, mortality elevations persisted for about three weeks in partially vaccinated and five weeks in fully vaccinated groups. Asymmetry between forward and reverse lag models suggested that mortality followed rather than preceded infection peaks. Conclusions: These findings demonstrate time linked mortality associations consistent with patterns seen in other population level datasets and warrant individual level investigation into potential mechanisms and clinical determinants.