Comparative effectiveness of the BNT162b2 and ChAdOx1 vaccines against Covid-19 in people over 50
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Abstract
Although pivotal trials with varying populations and study methods suggest higher efficacy for mRNA than adenoviral Covid-19 vaccines, not many studies have directly compared vaccine effectiveness in the population. Here, we conduct a head-to-head comparison of BNT162b2 versus ChAdOx1 against Covid-19. We analyse 235,181 UK Biobank participants aged 50 years or older and vaccinated with one or two doses of BNT162b2 or ChAdOx1. People are followed from the vaccination date until 18/10/2021. Inverse probability weighting is used to minimise confounding and the Cox models to derive hazard ratio. We find that, compared with one dose of ChAdOx1, vaccination with BNT162b2 is associated with a 28% (95% CI, 12-42) decreased risk of SARS-CoV-2 infection. Also, two doses of BNT162b2 vs ChAdOx1 confers 30% (95% CI, 25-35) and 29% (95% CI, 10-45) lower risks of both infection and hospitalisation during the study period when the Delta variant is dominant. Furthermore, the comparative protection against the infection persists for at least six months among the fully vaccinated, suggesting no differential waning between the two vaccines. These findings can inform evidence-based Covid-19 vaccination campaigns and booster strategies.
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SciScore for 10.1101/2021.12.18.21268039: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Ethics not detected. Sex as a biological variable To evaluate for potential heterogeneity of the comparative effectiveness among specific demographic subgroups and overtime after the second dose, we performed several secondary analyses by including multiplicative interaction terms between the vaccine types and the following categories separately: age (50-75 years or > 75 years), sex (male or female), ethnicity (white or other ethnic groups), BMI (< 25 vs ≥ 25), and four weeks’ consecutive time intervals. Randomization not detected. Blinding not detected. Power Analysis not detected. Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open …
SciScore for 10.1101/2021.12.18.21268039: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Ethics not detected. Sex as a biological variable To evaluate for potential heterogeneity of the comparative effectiveness among specific demographic subgroups and overtime after the second dose, we performed several secondary analyses by including multiplicative interaction terms between the vaccine types and the following categories separately: age (50-75 years or > 75 years), sex (male or female), ethnicity (white or other ethnic groups), BMI (< 25 vs ≥ 25), and four weeks’ consecutive time intervals. Randomization not detected. Blinding not detected. Power Analysis not detected. Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:Strengths and limitations: The leading challenges in estimating vaccine effectiveness with observational data lies in confounding by indication and potentially differential testing rates between exposed vaccinated and unvaccinated populations.18,19 However, our study minimized the impact of such differences by comparing two vaccines and restricting the analysis to a period when both vaccines were available and had a similar national delivery. UK data are ideal for comparative effectiveness research into Covid-19 vaccines, as both BNT162b2 and ChAdOx1 were rolled out simultaneously for the target population (adults ≥ 50 years) included in our analyses.20,21 ,22. However, additional limitations remain. Information on a few participants’ characteristics was collected ten years ago and may have changed since then. However, given that all people at the cohort recruitment were already middle-aged or older adults (40-69 years old), we expected any changes in those features such as socio-economic status and education are likely to be minor or unrelated to the choice of vaccine types. Admittedly, misclassification of covariates could bias the genuine association towards the null and lead to underestimating the comparative vaccine effectiveness. Our study has several unique strengths. First, the granularity of UK Biobank data and comprehensive linkage to external data sources allowed us to measure and control for an extensive array of confounders, including demographics, socio-e...
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
- Thank you for including a protocol registration statement.
Results from scite Reference Check: We found no unreliable references.
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