Transmission characteristics of SARS-CoV-2 variants of concern Rapid Scoping Review

  1. Janet Curran
  2. Justine Dol
  3. Leah Boulos
  4. Mari Somerville
  5. Holly McCulloch
  6. Marilyn MacDonald
  7. Jason LeBlanc
  8. Lisa Barrett
  9. Todd Hatchette
  10. Jeannette Comeau
  11. Bearach Reynolds
  12. Danielle Shin
  13. Allyson Gallant
  14. Helen Wong
  15. Daniel Crowther
  16. Ziwa Yu

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Abstract

Background

As of March 2021, three SARS-CoV-2 variants of concern (VOC) have been identified (B.1.1.7, B.1.351 and P.1) and been detected in over 111 countries. Despite their widespread circulation, little is known about their transmission characteristics. There is a need to understand current evidence on VOCs before practice and policy decisions can be made. This study aimed to map the evidence related to the transmission characteristics of three VOCs.

Methods

A rapid scoping review approach was used. Seven databases were searched on February 21, 2021 for terms related to VOCs, transmission, public health and health systems. A grey literature search was conducted on February 26, 2021. Title/abstracts were screened independently by one reviewer, while full texts were screened in duplicate. Data were extracted using a standardized form which was co-developed with infectious disease experts. A second data extractor verified the results. Studies were included if they reported on at least one of the VOCs and transmissibility. Animal studies and modeling studies were excluded. The final report was reviewed by content experts.

Results

Of the 1796 articles and 67 grey literature sources retrieved, 16 papers and 7 grey sources were included. Included studies used a wide range of designs and methods. The majority (n=20) reported on B.1.1.7. Risk of transmission, reported in 15 studies, was 45-71% higher for B.1.1.7 compared to non-VOCs, while R 0 was 75-78% higher and the reported R t ranged from 1.1-2.8. There was insufficient evidence on the transmission risk of B.1.35.1 and P.1. Twelve studies discussed the mechanism of transmission of VOCs. Evidence suggests an increase in viral load among VOCs based on cycle threshold values, and possible immune evasion due to increased ACE2 binding capacity of VOCs. However, findings should be interpreted with caution due to the variability in study designs and methods.

Conclusion

VOCs appear to be more transmissible than non-VOCs, however the mechanism of transmission is unclear. With majority of studies focusing on the B.1.1.7 VOC, more research is needed to build upon these preliminary findings. It is recommended that decision-makers continue to monitor VOCs and emerging evidence on this topic to inform public health policy.

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  1. ScreenIT

    SciScore for 10.1101/2021.04.23.21255515: (What is this?)

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

    Table 1: Rigor

    Ethicsnot detected.
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    In vitro changes in the binding affinity of spike protein receptor binding domain to the ACE2 receptor), changes in neutralization activity of anti-SARS-CoV-2 antibodies, and gene detection drop-outs like S-gene target failure (SGTF) in diagnostic assays.
    anti-SARS-CoV-2
    suggested: None
    Software and Algorithms
    SentencesResources
    The electronic database search was executed on February 21st, 2021 in MEDLINE, Embase, the Cochrane Database of Systematic Reviews (CDSR) and Central Register of Controlled Trials (CENTRAL), Epistemonikos’ L·OVE on COVID-19, and medRxiv and bioRxiv concurrently.
    MEDLINE
    suggested: (MEDLINE, RRID:SCR_002185)
    Embase
    suggested: (EMBASE, RRID:SCR_001650)
    Cochrane Database of Systematic Reviews
    suggested: None
    bioRxiv
    suggested: (bioRxiv, RRID:SCR_003933)

    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.

  2. Version published to 10.1101/2021.04.23.21255515 on medRxiv