Relative vaccine effectiveness against Delta and Omicron COVID-19 after homologous inactivated vaccine boosting: a retrospective cohort study

Lin Tang; Yanyang Zhang; Fuzhen Wang; Dan Wu; Zhao-Hui Qian; Rui Zhang; Ai-Bin Wang; Chang Huang; Haifeng Wang; Ying Ye; Mingxia Lu; Changshuang Wang; Ya-Ting Ma; Jingjing Pan; Ya-Fei Li; Xiao-Ya Lv; Zhijie An; Lance Rodewald; Xuan-Yi Wang; Yi-Ming Shao; Zhi-Yin Wu; Zundong Yin

doi:10.1136/bmjopen-2022-063919

Relative vaccine effectiveness against Delta and Omicron COVID-19 after homologous inactivated vaccine boosting: a retrospective cohort study

BMJ Open. 2022 Nov 11;12(11):e063919. doi: 10.1136/bmjopen-2022-063919.

Authors

Lin Tang^#¹, Yanyang Zhang^#², Fuzhen Wang¹, Dan Wu¹, Zhao-Hui Qian³, Rui Zhang⁴, Ai-Bin Wang⁵, Chang Huang^{1

6}, Haifeng Wang⁷, Ying Ye⁷, Mingxia Lu², Changshuang Wang², Ya-Ting Ma², Jingjing Pan⁷, Ya-Fei Li⁷, Xiao-Ya Lv⁸, Zhijie An¹, Lance Rodewald¹, Xuan-Yi Wang⁹, Yi-Ming Shao¹⁰, Zhi-Yin Wu¹¹, Zundong Yin¹²

Affiliations

¹ National Immunization Program, Chinese Center for Disease Control and Prevention, Beijing, China.
² Department of Henan Immunization Program, Henan Center for Disease Control and Prevention, Zhengzhou, Henan, China.
³ NHC Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
⁴ National Center for Clinical Laboratories, Beijing Hospital, National Center of Gerontology; Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, China.
⁵ Beijing Ditan Hospital Capital Medical University, Beijing, China.
⁶ China Field Epidemiology Training Program, Chinese Center for Disease Control and Prevention, Beijing, China.
⁷ Department of Communicable Disease Control and Prevention, Henan Provincial Center for Disease Control and Prevention, Zhengzhou, Henan, China.
⁸ Development Center for Medicine and Science & Technology, National Health Commission, Beijing, China.
⁹ Shanghai Institute of Infectious Disease and Biosecurity, Key Laboratory of Medical Molecular Virology of Minstry of Eduation & Ministry of Health, and Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai, China yinzd@chinacdc.cn yshao@chinaaids.cn zhiyinwu@126.com xywang@shmu.edu.cn.
¹⁰ State Key Laboratory of Infectious Disease Prevention and Control, National Center for AIDS/STD Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China yinzd@chinacdc.cn yshao@chinaaids.cn zhiyinwu@126.com xywang@shmu.edu.cn.
¹¹ Development Center for Medicine and Science & Technology, National Health Commission, Beijing, China yinzd@chinacdc.cn yshao@chinaaids.cn zhiyinwu@126.com xywang@shmu.edu.cn.
¹² National Immunization Program, Chinese Center for Disease Control and Prevention, Beijing, China yinzd@chinacdc.cn yshao@chinaaids.cn zhiyinwu@126.com xywang@shmu.edu.cn.

^# Contributed equally.

Abstract

ObjectiveTwo COVID-19 outbreaks occurred in Henan province in early 2022-one was a Delta variant outbreak and the other was an Omicron variant outbreak. COVID-19 vaccines used at the time of the outbreak were inactivated, 91.8%; protein subunit, 7.5%; and adenovirus5-vectored, 0.7% vaccines. The outbreaks provided an opportunity to evaluate variant-specific breakthrough infection rates and relative protective effectiveness of homologous inactivated COVID-19 vaccine booster doses against symptomatic infection and pneumonia.

Design: Retrospective cohort study METHODS: We evaluated relative vaccine effectiveness (rVE) with a retrospective cohort study of close contacts of infected individuals using a time-dependent Cox regression model. Demographic and epidemiologic data were obtained from the local Centers for Disease Control and Prevention; clinical and laboratory data were obtained from COVID-19-designated hospitals. Vaccination histories were obtained from the national COVID-19 vaccination dataset. All data were linked by national identification number.

Results: Among 784 SARS-CoV-2 infections, 379 (48.3%) were caused by Delta and 405 (51.7%) were caused by Omicron, with breakthrough rates of 9.9% and 17.8%, respectively. Breakthrough rates among boosted individuals were 8.1% and 4.9%. Compared with subjects who received primary vaccination series ≥180 days before infection, Cox regression modelling showed that homologous inactivated booster vaccination was statistically significantly associated with protection from symptomatic infection caused by Omicron (rVE 59%; 95% CI 13% to 80%) and pneumonia caused by Delta (rVE 62%; 95% CI 34% to 77%) and Omicron (rVE 87%; 95% CI 3% to 98%).

Conclusions: COVID-19 vaccination in China provided good protection against symptomatic COVID-19 and COVID-19 pneumonia caused by Delta and Omicron variants. Protection declined 6 months after primary series vaccination but was restored by homologous inactivated booster doses given 6 months after the primary series.

Keywords: COVID-19; Epidemiology; Immunology.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

COVID-19 Vaccines
COVID-19* / epidemiology
COVID-19* / prevention & control
Humans
Retrospective Studies
SARS-CoV-2
United States
Vaccine Efficacy
Vaccines, Inactivated

Substances

Vaccines, Inactivated
COVID-19 Vaccines

Supplementary concepts

COVID-19 vaccine booster shot
SARS-CoV-2 variants