Effectiveness of inactivated COVID-19 vaccines in preventing COVID-19-related hospitalization during the Omicron BF.7-predominant epidemic wave in Beijing, China: a cohort study.

Background: To estimate vaccine effectiveness(VE) against COVID-19-related hospitalization for inactivated vaccines during the Omicron BF.7-predominant epidemic wave in Beijing, China.

Methods: We recruited a cohort in Beijing on 17 and 18 December 2022, collected status of vaccination and COVID-19-related hospitalization since 1 November 2022 and prospectively followed until 9 January 2023. A Poisson regression model was used to estimate the VE.

Results: 16(1.15%) COVID-19-related hospitalizations were reported in 1391 unvaccinated participants; 7(0.25%) in 2765 participants with two doses, resulting in a VE of 70.89%(95% confidence interval[CI] 26.25 to 87.73); 32(0.27%) in 11,846 participants with three doses, with a VE of 65.25%(95% CI 32.24 to 81.83). The VE of three doses remained above 64% at 1 year or more since the last dose. Elderly people aged ≥ 60 years had the highest hospitalization incidence(0.66%), VE for two doses was 74.11%(95%CI: - 18.42 to 94.34) and VE for three doses was 80.98%(95%CI:52.83 to 92.33). We estimated that vaccination had averted 65,007(95%CI: 12,817 to 97,757) COVID-19-related hospitalizations among people aged ≥ 60 years during the BF.7-predominant period in Beijing.

Conclusion: Inactivated COVID-19 vaccines were effective against COVID-19-related hospitalization, especially for the elderly population who have increased risk of severe disease owing to SARS-CoV-2 infection.