Effectiveness of Inactivated COVID-19 Vaccines Against Symptomatic, Pneumonia, and Severe Disease Caused by the Delta Variant: Real World Study and Evidence — China, 2021
Dan Wu, Yanyang Zhang, Lin Tang, Fuzhen Wang, Ying Ye, Chao Ma, Hui Zheng, Wenzhou Yu, Lei Cao, Yifan Song, Abuduwaili Reyimu, Xiaoxiao Zhang, Haifeng Wang, Yifei Nie, Mingxia Lu, Muge Qi, Jun Li, Ruolin Wang, Kaichao Yang, Changshuang Wang, Lawrence Everett Rodewald, Geroge Fu Gao, Zhijie An, Zundong Yin, Henan Provincial Disease Control and Prevention, Zhengzhou, Henan, China
Abstract
WHAT IS ALREADY KNOWN ABOUT THIS TOPIC?: Effectiveness of China's 2 inactivated vaccines (BBIBP-CorV and CoronaVac) against pre-Delta severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) variants ranged from 47% to over 90%, depending on the clinical endpoint, and with greater effectiveness against more severe coronavirus disease 2019 (COVID-19). During an outbreak in Guangdong, inactivated vaccine effectiveness (VE) against the Delta variant was 70% for symptomatic infection and 100% for severe COVID-19. However, separate or combined VE estimates for the two inactivated vaccines against Delta are not available. WHAT IS ADDED BY THIS REPORT?: In an outbreak that started in a hospital, VEs of completed primary vaccination with inactivated COVID-19 vaccines against symptomatic COVID-19, COVID-19 pneumonia, and severe COVID-19 caused by the Delta variant were 51%, 61%, and 82%. Completed primary vaccination reduced the risk of progressing from mild to moderate or severe COVID-19 by 74%. VE estimates for BBIBP-CorV and CoronaVac or combined vaccination were similar, and partial vaccination was ineffective. WHAT ARE THE IMPLICATIONS FOR PUBLIC HEALTH PRACTICE?: Completed primary vaccination with either of the 2 inactivated COVID-19 vaccines reduces risk of symptomatic COVID-19, COVID-19 pneumonia, and severe COVID-19 caused by the Delta variant. Completion of the completed primary vaccination with two doses is necessary for protection from Delta.