Effectiveness of Inactivated COVID-19 Vaccines against Delta-Variant COVID-19: Evidence from an Outbreak in Inner Mongolia Autonomous Region, China

Autor: Chao Ma, Chang Huang, Wenrui Wang, Yudan Song, Xiaofeng Jiang, Xiaoling Tian, Boxi Liu, Fuli Chi, Shengli Lang, Dongyan Liu, Weiwei Sun, Lin Tang, Dan Wu, Yifan Song, Junhong Li, Lance Rodewald, Zundong Yin, Zhijie An
Jazyk: angličtina
Rok vydání: 2023
Předmět:
Zdroj: Vaccines, Vol 11, Iss 2, p 292 (2023)
Druh dokumentu: article
ISSN: 2076-393X
DOI: 10.3390/vaccines11020292
Popis: Phase 3 clinical trials and real-world effectiveness studies showed that China’s two main inactivated COVID-19 vaccines are very effective against serious illness. In November 2021, an outbreak occurred in the Inner Mongolia Autonomous Region that provided an opportunity to assess the vaccine effectiveness (VE) of these inactivated vaccines against COVID-19 caused by the delta variant. We evaluated VE with a retrospective cohort study of close contacts of infected individuals, using a generalized linear model with binomial distribution and log-link function to estimate risk ratios (RR) and VE. A total of 8842 close contacts were studied. Compared with no vaccination and adjusted for age, presence of comorbidity, and time since last vaccination, full vaccination reduced symptomatic infection by 62%, pneumonia by 64% and severe COVID-19 by 90%; reductions associated with homologous booster doses were 83% for symptomatic infection, 92% for pneumonia and 100% for severe COVID-19. There was no significant decline in two-dose VE for any outcome for up to 325 days following the last dose. There were no differences by vaccine brand. Inactivated vaccines were effective against delta-variant illness, and were highly effective against pneumonia and severe COVID-19; VE was increased by booster doses.
Databáze: Directory of Open Access Journals