Effectiveness of a third dose of BNT162b2 or mRNA-1273 vaccine for preventing post-vaccination COVID-19 infection: an observational study
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Abstract
BNT162b2 and mRNA-1273 vaccines are highly protective against COVID-19. Concern about waning immunity and reduced effectiveness against SARS-COV-2 variants led to use of a third dose six months after completing the primary series. We used data from the Veterans Health Administration to evaluate the effectiveness of a third dose of BNT162b2 or mRNA-1273 compared to the primary series in preventing post-vaccination COVID-19.
Methods
During January 1 - November 25, 2021, third dose recipients were matched (1:1) to demographically similar controls who did not receive a third dose. Eligible participants had completed the primary series at least six months (180 days) before recruitment date and had received at least one SARS-CoV-2 PCR test. Long-term care residents were excluded. Primary outcomes were documented SARS-CoV-2 infection and COVID-19 hospitalization. Effectiveness was estimated as 1-incidence rate ratio.
Findings
Following matching, the BNT162b2 group included 74,032 pairs and the mRNA-1273 group included 55,098 pairs. In BNT162b2 and mRNA-1273 groups, median age was 72 (interquartile range [IQR]: 64-75) and 72 (IQR: 66-77) years, 69,426 (93.8%) and 52,241 (94.8%) were male, and 43,039 (58.1%) and 37,218 (67.5%) were non-Hispanic White, respectively. Effectiveness of a third dose of BNT162b2 or mRNA-1273 compared to the primary series was 45.7% (95% confidence interval [CI]: 37.9-52.5%) and 46.6% (95% CI: 36.4-55.3%) for documented SARS-CoV-2 infection and 44.8% (95% CI: 26.6-58.4%) and 50.0% (95% CI: 26.2-66.1%) for COVID-19 hospitalization, respectively.
Interpretation
A third dose of BNT162b2 or mRNA-1273 is moderately effective against post-vaccination COVID-19 infection compared to the primary series.
Funding
None.
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SciScore for 10.1101/2021.11.29.21266777: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Ethics IRB: This project was approved by the Stanford University Institutional Review Board (Protocol ID 47191, “Public Health Surveillance in the Department of Veterans Affairs”) and written informed consent was waived.
Consent: This project was approved by the Stanford University Institutional Review Board (Protocol ID 47191, “Public Health Surveillance in the Department of Veterans Affairs”) and written informed consent was waived.Sex as a biological variable not detected. 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 …
SciScore for 10.1101/2021.11.29.21266777: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Ethics IRB: This project was approved by the Stanford University Institutional Review Board (Protocol ID 47191, “Public Health Surveillance in the Department of Veterans Affairs”) and written informed consent was waived.
Consent: This project was approved by the Stanford University Institutional Review Board (Protocol ID 47191, “Public Health Surveillance in the Department of Veterans Affairs”) and written informed consent was waived.Sex as a biological variable not detected. 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:Our findings are subject to several limitations. Clinical records for patients who received care in facilities external to VHA might not be available in VHA databases unless these services were ordered by VHA providers and paid for by VHA; therefore, these testing episodes and outcomes would be missed in our analysis. Although VHA issued national testing guidelines, differences across VHA facilities in testing assays and local policies or approaches to testing may contribute to variability in detection of vaccine breakthrough events; some events might have been missed or misclassified. Our study population consists of predominantly older, male persons; therefore, our results might not be generalizable to the larger US population. Though we sought to control for health-seeking behavior as well as demographic and clinical covariates associated with COVID-19, unmeasured confounders might affect our findings. To reduce residual confounding, we excluded long term care residents; our findings might not be applicable to this subgroup. Though we observed modest effectiveness of a third dose of vaccine in reducing post-vaccination infection, we were unable to assess associations with broader epidemiological outcomes such as reduced transmission among contacts. Given the observational nature of this study, data describing additional biomarkers, timing of exposures, symptoms, and the specific variants occurring in vaccine breakthrough events were unavailable; therefore, we were unable t...
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.
- No funding statement was detected.
- No protocol registration statement was detected.
Results from scite Reference Check: We found no unreliable references.
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