ABSTRACT
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 1 to 30 September 2021 to compare VE between the ‘early’ (fully vaccinated in April to June 2021) and ‘late’ (July to 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 three to five months of full vaccination for both BNT162b2 and CoronaVac vaccines in Malaysia. For CoronaVac, protection against ICU admission also declined.
ABSTRACT
Evaluation of vaccine effectiveness over time against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or coronavirus disease 2019 (COVID-19) is important. Evidence on effectiveness over time for the CoronaVac vaccine is lacking despite its widespread use globally. In Malaysia, a diverse set-up of COVID-19 vaccines was rolled out nationwide, and the waning of vaccine protection is a concern. We aimed to investigate and compare waning vaccine effectiveness against COVID-19 infections, COVID-19 related ICU admission and COVID-19 related deaths for BNT162b2 and CoronaVac vaccines. In this observational study, we consolidated nationally representative data on COVID-19 vaccination and patients' outcomes. Data on all confirmed COVID-19 cases from 1 to 30 September 2021 were used to compare vaccine effectiveness between the 'early' group (fully vaccinated in April to June 2021) and the 'late' group (fully vaccinated in Jul to Aug 2021). We used a negative binomial regression model to estimate vaccine effectiveness against COVID-19 infections for both 'early' and 'late' groups, by comparing the rates of infection for individuals vaccinated in the two different periods relative to the unvaccinated. Among confirmed COVID-19 cases, we used logistic regression to estimate and compare vaccine effectiveness against ICU admission and deaths between the two different periods. For BNT162b2, vaccine effectiveness against COVID-19 infections declined from 90.8% (95% CI 89.4, 92.0) in the late group to 79.1% (95% CI 75.8, 81.9) in the late group. Vaccine effectiveness for BNT162b2 against ICU admission and deaths were comparable between the two different periods. For CoronaVac, vaccine effectiveness waned against COVID-19 infections from 74.4% in the late group (95% CI 209 70.4, 77.8) to 30.0% (95% CI 18.4, 39.9) in the early group. It also declined significantly against ICU admission, dropping from 56.1% (95% CI 51.4, 60.2) to 29.9% (95% CI 13.9, 43.0). For deaths, however, CoronaVac's effectiveness did not wane after three to five months of full vaccination. Vaccine effectiveness against COVID-19 infections waned after three to five months of full vaccination for both BNT162b2 and CoronaVac in Malaysia. Additionally, for CoronaVac, protection against ICU admission declined as well. Evidence on vaccine effectiveness over time informs evolving policy decisions on vaccination.