Relative effectiveness of the second booster COVID-19 vaccines against laboratory confirmed SARS-CoV-2 infection in healthcare workers: VEBIS HCW VE cohort study (1 October 2022-2 May 2023)

The bivalent COVID-19 could have reduced the risk of SARS-CoV-2 infection among HCWs by 11 %. However, we note the limitation of imprecise rVE estimates due to the proportion of monovalent vaccine used in the study, the small sample size and the study being conducted during the predominant circulation of XBB.1.5 sub-lineage. COVID-19 vaccine effectiveness studies in HCWs can provide important evidence to inform the optimal timing and the use of updated COVID-19 vaccines.