Effectiveness of Inactivated COVID-19 Vaccination Against COVID-19–Related Hospitalization and Severe Outcomes in Adults ≥80 Years During Omicron Circulation in Beijing, China: Retrospective Cohort Study

Dan Zhao   ^{1, 2, 3 *} , MD ;   Ying Ma   ^{1, 2, 3 *} , MD ;   Juan Li   ^{1, 2, 3} , PhD ;   Xiaomei Li   ^{1, 2, 3} , BSc ;   Zhiqiang Cao   ^{1, 2, 3} , PhD ;   Wei Yao   ¹ , BSc ;   Jiang Wu   ^{1, 2} , MD ;   Luodan Suo   ^{1, 2, 3} , MD

¹ Beijing Key Laboratory of Surveillance, Early Warning and Pathogen Research on Emerging Infectious Diseases, Beijing Center for Disease Prevention and Control, Beijing, China

² Beijing Research Center for Respiratory Infectious Diseases, Beijing, China

³ School of Public Health, Capital Medical University, Beijing, China

*these authors contributed equally