4.5 Article

Effectiveness of Inactivated COVID-19 Vaccines Against Symptomatic, Pneumonia, and Severe Disease Caused by the Delta Variant: Real World Study and Evidence - China, 2021

Journal

CHINA CDC WEEKLY
Volume 4, Issue 4, Pages 57-65

Publisher

Chinese Center for Disease Control and Prevention
DOI: 10.46234/ccdcw2022.009

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In an outbreak from a hospital setting, completion of primary vaccination with inactivated COVID-19 vaccines reduces the risk of symptomatic COVID-19, COVID-19 pneumonia, and severe COVID-19 caused by the Delta variant. Partial vaccination is ineffective, and completion of two doses of the primary vaccination is necessary for protection from Delta.
What is already known about this topic? Effectiveness of China's 2 inactivated vaccines (BBIBPCorV and CoronaVac) against pre-Delta severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) variants ranged from 47% to over 90%a, 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 WE) 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 GOVID-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.

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