Background rates of all-cause mortality, hospitalizations, and emergency department visits among nursing home residents in Ontario, Canada to inform COVID-19 vaccine safety assessments

Sundaram, M.; Nasreen, S.; Calzavara, A.; He, S.; Chung, H.; Bronskill, S. E.; Buchan, S. A.; Tadrous, M.; Tanuseputro, P.; Wilson, K.; Wilson, S.; Kwong, J.; Investigators, Canadian Immunization Research Network

Background. Nursing home (NH) residents have been disproportionately affected by the coronavirus disease 2019 (COVID-19) pandemic and are prioritized for vaccination. NH residents are generally at increased risk of poor outcomes due to advanced age, frailty, and complex health conditions. We report monthly incidence rates of deaths, hospitalizations, and emergency department (ED) visits during ten pre-pandemic years (2010-2019) and 2020 to provide context for assessments of COVID-19 vaccine safety in NH residents. Methods. We observed deaths, hospitalizations, and ED visits among all Ontarians living in NHs using health administrative databases. Monthly incidence rates were calculated by month, by sex, and by age group. Direct comparisons between months were assessed using one-sample t-tests; direct comparisons by age and sex were assessed using chi-squared tests. Results. From January 1, 2010 through December 31, 2019, there were, on average, 83,453 (SD: 652.4) Ontarians living in NHs in any given month, with an average of 2.3 (SD: 0.28) deaths, 3.1 (SD: 0.16) hospitalizations, and 3.6 (SD: 0.17) ED visits per 100 residents per month. Mortality rates were higher for men (p<0.001) and residents aged [≥]80 years (p<0.001). Hospitalization and ED visit rates were higher for men but were lower for residents aged [≥]80 years. From January to October 2020, the number of NH residents declined markedly. Mortality rates were increased in 2020 compared to 2010-2019, but hospitalization and ED visit rates were reduced in 2020 compared to 2010-2019 (p<0.001). Conclusion. We identified relatively consistent monthly mortality, hospitalization, and ED visit rates during ten pre-pandemic years. Marked differences in these rates were observed during 2020, coinciding with heightened COID-19 infection rates and restrictions. These results provide context to the assessment of COVID-19 vaccine safety outcomes in this high-risk population.