Estimating the Waning Effectiveness of COVID-19 Vaccines From Population-Level Surveillance Data in Hong Kong

Abstract Assessing the time-varying effectiveness of coronavirus disease 2019 (COVID-19) vaccines is critical to guiding vaccine strategies and public health policies. We developed a Bayesian framework to estimate the waning vaccine effectiveness of various doses of CoronaVac and Comirnaty based on population-level surveillance data. We applied this framework to data on a large Omicron BA.2 epidemic in Hong Kong from January to May 2022. Our results indicated that despite high vaccination rates during this period, high vaccine uptake mitigated but did not prevent rapid spread of infection.