JMIR Publications

ABSTRACT

Background:

A large wave of COVID-19 caused by SARS-CoV-2 Omicron subvariants began in Beijing in early December 2022.

Objective:

We evaluated the COVID-19 vaccine effectiveness (VE) in mitigating the risk of COVID-19-related hospitalization during the epidemic.

Methods:

We conducted a retrospective cohort study linking regional healthcare data and vaccination registry routinely collected in Beijing. All electronical medical records on COVID-19 related hospital discharges of the elderly inpatients aged 80 years and over during November 2022 and February 2023 were included in the study. Poisson regressions were used to estimate incidence risk ratio (IRR) of COVID-19 related-hospitalization or death. VE was calculated as 1 minus IRR ×100%.

Results:

A total of 53,789 individuals aged 80 and above were included, 30531 individuals were in the vaccine group (56.76%) and 23258 individuals in the unvaccinated group (43.24%). 17916 (33.31%) were diagnosed with COVID-19. The analysis revealed that the VE of booster vaccination in preventing COVID-19-related hospital, severe/critical COVID-19 and in-hospital death were 63.5% (95%CI: 59.8%–66.9%), 66.9% (95%CI: 60.1%–72.6%) and 79.4% (95%CI: 77.0%–81.5%), the VE of primary series were 56.0% (95%CI:51.4%–60.2%), 66.8% (95%CI:59.0%–73.0%) and 66.4% (95%CI: 63.0%–69.5%).

Conclusions:

Booster vaccination significantly reduced the risk of COVID-19-related hospitalization, critical illness or in-hospital deaths in the elderly inpatients during an Omicron dominant period. Offering booster dose and regularly monitoring the coverage and VE of COVID-19 vaccines remains the main stay for mitigating impacts of upcoming epidemics.