Abstract

Randomized clinical trials have shown mRNA-based vaccines to be 92-95% effective to prevent COVID-19 in adults. We aimed to estimate the impact of vaccination on the risk of severe COVID-19 (requiring hospitalization) in elderly people.

Each 1,422,461 vaccinated subject aged 75 and older was matched to two unvaccinated subjects of same age, sex, administrative region, and type of residence. They were followed from date of first injection between 27 December 2020 and 24 February 2021 to 20 March 2021 for COVID-19 hospitalization. Mean age was 82.4 years (SD, 5.7) and median follow-up was 38 days [IQR, 17 – 54].

Adjusted Hazard Ratio for COVID-19 hospitalization from day 7 after the second dose was estimated at 0.14 (95% confidence interval, 0.11 to 0.17), i.e. an estimated 86% risk reduction in people aged 75 and older, highlighting the major impact of mRNA vaccination on reducing the risk of COVID-19 among elderly people.