The efficacy and effectiveness of individual vaccine products for COVID-19 and its variants of concern are well known. However, research on the effectiveness of multidose vaccine regimens and combinations, especially for populations such as older people and those who are immunocompromised, is lacking.

A research team from The Chinese University of Hong Kong (CUHK)’s Faculty of Medicine (CU Medicine) is the first to perform a comprehensive study with a large sample size to compare the vaccine efficacies of 24 combinations of COVID-19 vaccine regimens comprising seven types of vaccines worldwide.

Results showed a three-dose mRNA regimen significantly decreases the risk of immunocompromised and elderly patients developing asymptomatic or symptomatic COVID-19 infections; and, most importantly, a third dose of the vaccine is required to protect against Omicron infection.

The findings will aid in formulating public health policy, clinical recommendations to patients and research on COVID-19 vaccination.

Professor Peter Pak Hang CHEUNG, Assistant Professor of the Department of Chemical Pathology at CU Medicine said, “Our findings provide estimates of the efficacy of 24 different COVID-19 vaccine regimens, which will aid significantly in formulating public health policy, providing clinical recommendations to patients and research on COVID-19 vaccination. We will update the results when new published studies or preprints become available.”