Waning COVID-19 Vaccine Effectiveness for BNT162b2 and CoronaVac in Malaysia: An Observational Study

Objectives: We aimed to investigate and compare waning vaccine effectiveness (VE) against COVID-19 infection, COVID-19 related ICU admission, and COVID-19-related death for BNT162b2 and CoronaVac vaccines.

Methods: We consolidated national data on COVID-19 vaccination and outcomes, and used cases from September 1^st-30^th, 2021 to compare VE between the 'early' (fully vaccinated in April-June 2021) and 'late' (July-August 2021) groups. We estimated VE against COVID-19 infection with a negative binomial regression and VE against ICU admission and death among confirmed COVID-19 cases with a logistic regression.

Results: For BNT162b2, VE against COVID-19 infections declined from 90.8% (95% CI 89.4, 92.1) in the 'late' group to 79.3% (95% CI 76.1, 82.1) in the 'early' group. VE for BNT162b2 against ICU admission and death were stable. For CoronaVac, VE waned against COVID-19 infections from 74.5% (95% CI 70.6, 78.0) to 30.4% (95% CI 18.8, 40.3). Effectiveness against ICU admission waned from 56.0% (95% CI 51.2, 60.2) to 28.7% (95% CI 12.2, 42.1). CoronaVac's effectiveness against death remained stable.

Conclusion: VE against COVID-19 infection waned after 3-5 months of full vaccination for both BNT162b2 and CoronaVac vaccines in Malaysia. For CoronaVac, protection against ICU admission also declined.