Effectiveness of mRNA COVID-19 vaccines against Omicron and Delta variants in a matched test-negative case–control study among US veterans

  1. Yinong Young-Xu
  2. Gabrielle M Zwain
  3. Hector S Izurieta
  4. Caroline Korves
  5. Ethan I Powell
  6. Jeremy Smith
  7. Abirami Balajee
  8. Mark Holodniy
  9. David O Beenhouwer
  10. Maria C Rodriguez-Barradas
  11. Sheldon T Brown
  12. Vincent C Marconi

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Abstract

To estimate the effectiveness of messenger RNA (mRNA) booster doses during the period of Delta and Omicron variant dominance.

Design

We conducted a matched test-negative case–control study to estimate the vaccine effectiveness (VE) of three and two doses of mRNA vaccines against infection (regardless of symptoms) and against COVID-19-related hospitalisation and death.

Setting

Veterans Health Administration.

Participants

We used electronic health record data from 114 640 veterans who had a SARS-CoV-2 test during November 2021–January 2022. Patients were largely 65 years or older (52%), male (88%) and non-Hispanic white (59%).

Main outcome measures

First positive result for a SARS-CoV-2 PCR or antigen test.

Results

Against infection, booster doses had higher estimated VE (64%, 95% CI 63 to 65) than two-dose vaccination (12%, 95% CI 10 to 15) during the Omicron period. For the Delta period, the VE against infection was 90% (95% CI 88 to 92) among boosted vaccinees, higher than the VE among two-dose vaccinees (54%, 95% CI 50 to 57). Against hospitalisation, booster dose VE was 89% (95% CI 88 to 91) during Omicron and 94% (95% CI 90 to 96) during Delta; two-dose VE was 63% (95% CI 58 to 67) during Omicron and 75% (95% CI 69 to 80) during Delta. Against death, the VE with a booster dose was 94% (95% CI 90 to 96) during Omicron and 96% (95% CI 87 to 99) during Delta.

Conclusions

Among an older, mostly male, population with comorbidities, we found that an mRNA vaccine booster was highly effective against infection, hospitalisation and death. Although the effectiveness of booster vaccination against infection was moderately higher against Delta than against the Omicron SARS-CoV-2 variant, effectiveness against severe disease and death was similarly high against both variants.

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  1. Version published to 10.1136/bmjopen-2022-063935
  2. Version published to 10.1101/2022.01.15.22269360v2 on medRxiv
  3. ScreenIT

    SciScore for 10.1101/2022.01.15.22269360: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    EthicsIRB: The study was approved by the institutional review board of the Department of Veterans Affairs Medical Center in White River Junction, Vermont, and was granted an exemption for consent because it was deemed impractical.
    Consent: The study was approved by the institutional review board of the Department of Veterans Affairs Medical Center in White River Junction, Vermont, and was granted an exemption for consent because it was deemed impractical.
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    Data analysis was performed using SAS 9.4 (SAS Institute, Cary, North Carolina).
    SAS Institute
    suggested: (Statistical Analysis System, RRID:SCR_008567)

    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: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.

    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.
    • No protocol registration statement was detected.

    Results from scite Reference Check: We found no unreliable references.

    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  4. Version published to 10.1101/2022.01.15.22269360v1 on medRxiv