Effectiveness of Inactivated COVID-19 Vaccines against COVID-19 Caused by the SARS-CoV-2 Delta and Omicron Variants: A Retrospective Cohort Study
Qiaoli Hua,
Danwen Zheng,
Bo Yu,
Xinghua Tan,
Qiumin Chen,
Longde Wang,
Jing Zhang,
Yuntao Liu,
Heng Weng,
Yihang Cai,
Xiaohua Xu,
Bing Feng,
Guangjuan Zheng,
Banghan Ding,
Jianwen Guo,
Zhongde Zhang
Affiliations
Qiaoli Hua
The Second Clinical College, Guangzhou University of Chinese Medicine, Guangzhou 510006, China
Danwen Zheng
Department of Emergency, the Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510120, China
Bo Yu
Department of General Surgery, The No.2 People’s Hospital of Lanzhou, Lanzhou 730030, China
Xinghua Tan
Department of Traditional Chinese Medicine, Guangzhou Eighth People’s Hospital, Guangzhou Medical University, Guangzhou 510060, China
Qiumin Chen
Department of Traditional Chinese Medicine, Xinglin District, The First Affiliated Hospital of Xiamen University, Xiamen 361022, China
Longde Wang
Affiliated Hospital of Gansu University of Traditional Chinese Medicine, Lanzhou 730020, China
Jing Zhang
Department of Respiratory and Critical Care Medicine, Xiamen Hospital of Traditional Chinese Medicine, Xiamen 361000, China
Yuntao Liu
Department of Emergency, the Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510120, China
Heng Weng
State Key Laboratory of Dampness Syndrome of Chinese Medicine, Guangzhou 510120, China
Yihang Cai
The Second Clinical College, Guangzhou University of Chinese Medicine, Guangzhou 510006, China
Xiaohua Xu
Department of Emergency, the Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510120, China
Bing Feng
Department of Pharmacology of Traditional Chinese Medicine, the Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510120, China
Guangjuan Zheng
Department of Pharmacology of Traditional Chinese Medicine, the Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510120, China
Banghan Ding
Department of Emergency, the Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510120, China
Jianwen Guo
Guangdong Provincial Key Laboratory of Research on Emergency in Traditional Chinese Medicine, Guangzhou 510120, China
Zhongde Zhang
Department of Emergency, the Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510120, China
Background: Real-world evidence on the effectiveness of inactivated vaccines against the Delta and Omicron (BA.2.38) variants remains scarce. Methods: A retrospective cohort study was conducted to estimate the adjusted vaccine effectiveness (aVE) of one, two, and three doses of inactivated vaccines in attenuating pneumonia, severe COVID-19, and the duration of viral shedding in Delta and Omicron cases using modified Poisson and linear regression as appropriate. Results: A total of 561 COVID-19 cases were included (59.2% Delta and 40.8% Omicron). In total, 56.4% (184) of Delta and 12.0% (27) of Omicron cases had COVID-19 pneumonia. In the two-dose vaccinated population, 1.4% of Delta and 89.1% of Omicron cases were vaccinated for more than 6 months. In Delta cases, the two-dose aVE was 52% (95% confidence interval, 39–63%) against pneumonia and 61% (15%, 82%) against severe disease. Two-dose vaccination reduced the duration of viral shedding in Delta cases, but not in booster-vaccinated Omicron cases. In Omicron cases, three-dose aVE was 68% (18%, 88%) effective against pneumonia, while two-dose vaccination was insufficient for Omicron. E-values were calculated, and the E-values confirmed the robustness of our findings. Conclusions: In Delta cases, two-dose vaccination within 6 months reduced pneumonia, disease severity, and the duration of viral shedding. Booster vaccination provided a high level of protection against pneumonia with Omicron and should be prioritized.
