Averted mortality by COVID-19 vaccination in Belgium between 2021 and 2023

ABSTRACT Background Vaccination campaigns were rolled out primarily to limit the impact of COVID-19 on severe health outcomes, including mortality. Aim We aimed to estimate the number of averted deaths by COVID-19 vaccination in the Belgian population aged 65 years and older, between January 2021 and January 2023. Methods Nationwide data on COVID-19 infections, vaccine administrations and all-cause mortality were individually linked. We estimated Vaccine Effectiveness against COVID-19 mortality (VE) among persons having received a vaccine dose in the last 6 months, using a Cox proportional hazards model adjusted for age, sex, time since vaccination, previous infection, underlying health conditions, province and income. COVID-19 death was defined as a person with a laboratory-confirmed SARS-CoV-2 infection who died within a specified interval. Based on obtained VE estimates, vaccine coverage and national COVID-19 mortality data, we estimated the number of averted deaths. Results We estimated VE (0-59 days after vaccination) for 65-79 year and ≥80 year-olds respectively, at 81.9% (78.1%-85.1%) and 74.7% (71.2%-77.7%) during Alpha, at 90.5% (88.8%-91.9%) and 91.4% (90.4%- 92.4%) during Delta and at 84.0% (81.8%-85.9%) and 74.5% (72.4%-76.5%) during Omicron period. Among the Belgian population aged 65 years and older, we estimated 12,806 deaths averted (11,633- 13,982), representing a 54% reduction (51%-56%) in the expected deaths (without vaccination). During the Delta period COVID-19 deaths were reduced by 68%, during Omicron by 54% and during Alpha by 31%. Discussion Vaccinating against COVID-19 reduced deaths by 54% among the Belgian population aged 65 years and older, underscoring the importance of COVID-19 vaccines in reducing mortality.