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.