Impact of vaccination on new SARS-CoV-2 infections in the United Kingdom

  1. Emma Pritchard
  2. Philippa C. Matthews
  3. Nicole Stoesser
  4. David W. Eyre
  5. Owen Gethings
  6. Karina-Doris Vihta
  7. Joel Jones
  8. Thomas House
  9. Harper VanSteenHouse
  10. Iain Bell
  11. John I. Bell
  12. John N. Newton
  13. Jeremy Farrar
  14. Ian Diamond
  15. Emma Rourke
  16. Ruth Studley
  17. Derrick Crook
  18. Tim E. A. Peto
  19. A. Sarah Walker
  20. Koen B. Pouwels

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Abstract

The effectiveness of COVID-19 vaccination in preventing new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in the general community is still unclear. Here, we used the Office for National Statistics COVID-19 Infection Survey—a large community-based survey of individuals living in randomly selected private households across the United Kingdom—to assess the effectiveness of the BNT162b2 (Pfizer–BioNTech) and ChAdOx1 nCoV-19 (Oxford–AstraZeneca; ChAdOx1) vaccines against any new SARS-CoV-2 PCR-positive tests, split according to self-reported symptoms, cycle threshold value (<30 versus ≥30; as a surrogate for viral load) and gene positivity pattern (compatible with B.1.1.7 or not). Using 1,945,071 real-time PCR results from nose and throat swabs taken from 383,812 participants between 1 December 2020 and 8 May 2021, we found that vaccination with the ChAdOx1 or BNT162b2 vaccines already reduced SARS-CoV-2 infections ≥21 d after the first dose (61% (95% confidence interval (CI) = 54–68%) versus 66% (95% CI = 60–71%), respectively), with greater reductions observed after a second dose (79% (95% CI = 65–88%) versus 80% (95% CI = 73–85%), respectively). The largest reductions were observed for symptomatic infections and/or infections with a higher viral burden. Overall, COVID-19 vaccination reduced the number of new SARS-CoV-2 infections, with the largest benefit received after two vaccinations and against symptomatic and high viral burden infections, and with no evidence of a difference between the BNT162b2 and ChAdOx1 vaccines.

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  1. Version published to 10.1038/s41591-021-01410-w
  2. ScreenIT

    SciScore for 10.1101/2021.04.22.21255913: (What is this?)

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

    Table 1: Rigor

    EthicsConsent: Following verbal agreement to participate, a study worker visited each selected household to take written informed consent for individuals aged 2 years and over.
    Sex as a biological variablenot detected.
    RandomizationPrivate households are randomly selected on a continuous basis from address lists and previous surveys to provide a representative sample across the UK.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    Blood samples were couriered directly to the University of Oxford, where they were tested for the SARS-CoV-2 antibody using an ELISA detecting anti-trimeric spike IgG19.
    anti-trimeric spike IgG19
    suggested: None
    Software and Algorithms
    SentencesResources
    After this, it used a commercialised CE-marked version of the assay, the Thermo Fisher OmniPATH 384 Combi SARS-CoV-2 IgG ELISA (Thermo Fisher Scientific, Waltham, MA, USA), with the same antigen and a colorimetric detection system (positivity threshold 42 ng/ml monoclonal antibody unit equivalents, determined from 3840 samples run in parallel).
    Thermo Fisher OmniPATH
    suggested: None

    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 weaknesses of the study: The main study strength is its design as a large-scale community survey recruiting from randomly selected private residential households, providing a representative sample of the UK general population. Participants are tested regardless of symptoms, allowing us to additionally consider vaccine effectiveness against infection without reported symptoms. The availability of Ct values allowed us to compare vaccine impact on viral loads, using Ct as a proxy30. Scheduled visits provide an unbiased sampling frame which we exploited for our logistic regression, rather than having to censor individuals at last tests in the study using time-to-event analyses, and assume all infections between visits were identified. Participants were asked about demographics, behaviours, and work, allowing us to control for a wide range of potential confounders that are unavailable in record linkage studies performed to date.15 The design also has limitations, particularly with individuals tested initially at weekly and then monthly visits. Any positive episodes occurring between visits will be missed, leading to contamination of the “not vaccinated, no previous PCR/antibody-positive” groups, possibly diluting the effect of vaccination. Because participants can only test positive at scheduled visits, some of the “new” positives episodes may in fact have occurred sometime previously; we therefore stratified time from vaccination to reduce the impact of this. Older ...

    Results from TrialIdentifier: We found the following clinical trial numbers in your paper:

    IdentifierStatusTitle
    ISRCTN21086382NANA

    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.

    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.

  3. Version published to 10.1101/2021.04.22.21255913 on medRxiv