Feasibility of Booster Vaccination in High-Risk Populations for Controlling Coronavirus Variants - China, 2021

Introduction: Vaccination booster shots are completely necessary for controlling breakthrough infections of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in China. The study aims to estimate effectiveness of booster vaccines for high-risk populations (HRPs). Methods: A vaccinated Susceptible-Exposed-Symptomatic- Asymptomatic-Recovered/ Removed (SEIAR) model was developed to simulate scenarios of effective reproduction number (R-eff) from 4 to 6. Total number of infectious and asymptomatic cases were used to evaluated vaccination effectiveness. Results: Our model showed that we could not prevent outbreaks when covering 80% of HRPs with booster unless R-eff=4.0 or the booster vaccine had efficacy against infectivity and susceptibility of more than 90%. The results were consistent when the outcome index was confirmed cases or asymptomatic cases. Conclusions: An ideal coronavirus disease 2019 (COVID-19) booster vaccination strategy for HRPs would be expected to reach the initial goal to control the transmission of the Delta variant in China. Accordingly, the recommendation for the COVID-19 booster vaccine should be implemented in HRPs who are already vaccinated and could prevent transmission to other groups.

Automated summary

The study findings suggest that unless booster vaccines have efficacy against infectivity and susceptibility of more than 90%, covering 80% of high-risk populations with booster vaccines may not fully prevent outbreaks of the SARS-CoV-2 virus. Therefore, implementing a COVID-19 booster vaccine strategy for high-risk populations who are already vaccinated is recommended to control the transmission of virus variants in China.