Time from last immunity event against infection during Omicron dominant period in Malaysia.

We used a multi-centred, prospective cohort to study 482 two-dose and three-dose BNT162b2 vaccinated healthcare workers (HCWs) for SARS-CoV-2 infection during the Omicron dominant period in Malaysia. Between January 31 and July 31, 2022, the cumulative incidence was 44.6% (95%CI 40.2 - 49.1%) and the incidence rate was 3.33 (95% CI 2.91-3.80) per 1000 person-days. Our study found that protection against Omicron infection was significantly higher for persons with previous SARS-CoV-2 infection (hazard ratio (HR) 0.41, 95%CI 0.27 - 0.62) and persons with a more recent immunity event (<30 days [reference] vs >90 days, HR 3.82, 95%CI 1.34 - 10.90) from the beginning of Omicron period.