Enhanced neutralization against SARS-CoV-2 by vaccine booster exhibits reduction of Omicron variant

Abstract

The Omicron Variant of concern (B.1.1.529) has spread internationally and is raising serious concerns about the reduced vaccine efficacy and the increased risk of reinfection. Here we assessed the serum neutralizing activity using a pseudovirus-based neutralization assay in 292 healthcare workers who had administered a third homologous boosting vaccination 8 to 9 months after completion of the priming two-dose inactivated vaccination to investigate whether the newly identified Omicron variant could escape serum antibody neutralization elicited by the booster vaccination. The third booster dose with BBIBP-CorV could enhance the neutralizing immune response against SARS-CoV-2, and the neutralization GMT on day 28 after the third booster dose was 6.1 times higher than the GMT on day 28 after the second dose. The Omicron variant did cause significantly lower neutralization sensitivity compared to the wild-type strain of the booster elicited serum, with about 20.1-fold reduction. Our study demonstrated that a third booster dose of BBIBP-CorV lead to a significant rebound in neutralizing immune response against SARS-CoV-2, while the Omicron variant showed extensive but incomplete escape of the booster elicited neutralization.