ABSTRACT
Introduction: As of 29 July 2022, SARS-CoV-2 has infected 4.7 million Malaysians. Reinfection, defined as a new infection 90 days from initial infection is now rising due to the emergence of new variants. Studies have shown that healthcare workers (HCW) are 3.4 times more likely to test positive for COVID-19. This study aims to describe the reinfection rate of COVID-19 and protection effectiveness (PE) from past infection among HCWs in public hospitals in Malaysia. Method(s): A prospective cohort study was conducted from March 2021. HCWs were followed up to determine the post BNT162b2 vaccination humoral response to SARS-CoV-2. Additionally, participants were prompted to self-report a positive COVID-19 result. Reinfection rates were calculated using the total number of patients who had a prior infection as denominator. Infection rates were analysed at a predetermined period throughout our follow-up. Protection offered by prior infection was calculated as one minus the ratio of infection rate for COVID-19 positive patients and COVID-19 naive patients (1 - RR x 100%). Result(s): In this cohort, the cumulative incidence rate for SARS-CoV-2 is 44.6% (246/551). Reinfection rate is 6.5% (16/246). The PE at 3 and 6 months were 100% respectively while the PE at 9 and 12 months were 72.1% and 56.2%. Conclusion(s): Past infection offers 100% protection against reinfection up to 6 months but this protection steadily declines with the emergence of Omicron variant, even among vaccinated and boosted individuals. As variant-specific vaccines are still in development, reducing exposure and compliance to COVID-19 prevention guidelines are imperative to avoid infection.