Booster dose of BNT162b2 after two doses of CoronaVac improves neutralization of SARS-CoV-2 Omicron variant

Background: The emergence of the SARS-CoV-2 Omicron variant, with numerous mutations, raised concerns about vaccine escape, particularly reduced neutralization by vaccine-induced antibodies. Methods: Using viral microneutralization assays, antibody neutralization against Omicron was evaluated in 90 individuals who received a BNT162b2 mRNA booster after a two-dose CoronaVac primary series. Results: Seroconversion 30 and 60 days after the CoronaVac series was 16.6% and 10%, respectively. After the BNT162b2 booster, seroconversion increased to 76.6%, and the mean neutralization titer against Omicron increased 43.1-fold. Conclusions: A BNT162b2 booster following CoronaVac positively impacts the neutralizing antibody response against Omicron.