Modeling the Prediction on the Efficacy of a Homologous Third Dose of CoronaVac Against SARS-CoV-2 Omicron BA.1, BA.2, BA.2.12.1, and BA.4/5 — China, 2020–2021

WHAT IS ALREADY KNOWN ABOUT THIS TOPIC? Previous studies have reported vaccine efficacy or effectiveness against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron subvariants for several vaccine platforms. However, there are currently few data on estimates of inactivated platform coronavirus disease 2019 (COVID-19) vaccines, especially against the globally dominant subvariant — Omicron BA.5. WHAT IS ADDED BY THIS REPORT? The study predicts vaccine efficacy against four Omicron subvariants — Omicron BA.1, BA.2, BA.2.12.1, and BA.4/5 — after vaccination with a homologous third dose of CoronaVac across clinical endpoints and age groups. WHAT ARE THE IMPLICATIONS FOR PUBLIC HEALTH PRACTICE? The results suggest that CoronaVac-elicited immunity may not provide adequate protection against Omicron subvariants after the homologous third dose, and a heterologous booster and Omicron-specific vaccination may be alternative strategies.