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.
Subject(s)
COVID-19 , Coronavirus Infections , DeathABSTRACT
Objective This study aims to investigate the association between smoking and the severity of COVID-19 infection during the initial wave of this pandemic in Malaysia. Methods This is a multi-centre observational study using secondary hospital data collected retrospectively from 1st February 2020 until 30th May 2020. Clinical records of all real-time polymerase chain reaction (RT-PCR) confirmed COVID-19 cases with smoking status, co-morbidities, clinical features and disease management were retrieved. Severity was assessed by presence of complications and outcomes of COVID-19 infection. Logistic regression was used to determine the association between COVID-19 disease severity and smoking status. Results A total of 5889 COVID-19 cases were included in the analysis. Ever smokers had higher risk of having COVID-19 complications such as acute respiratory distress syndrome (OR: 1.69, 95% CI = 1.09 - 2.55), renal injury (OR: 1.55, 95% CI = 1.10 - 2.14) and acute liver injury (OR: 1.33, 95% CI = 1.01 - 1.74) compared to never smokers. However, in term of disease outcomes, there were no differences between two groups. Conclusion Although no significant association was found in term of disease outcomes, smoking is associated with higher risk of having complications due to COVID-19 infection.