Effect of vaccination on household transmission of SARS-CoV-2 Delta variant of concern

  1. Frederik Plesner Lyngse
  2. Kåre Mølbak
  3. Matt Denwood
  4. Lasse Engbo Christiansen
  5. Camilla Holten Møller
  6. Morten Rasmussen
  7. Arieh Sierra Cohen
  8. Marc Stegger
  9. Jannik Fonager
  10. Raphael Niklaus Sieber
  11. Kirsten Maren Ellegaard
  12. Claus Nielsen
  13. Carsten Thure Kirkeby

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Abstract

Effective vaccines protect individuals by not only reducing the susceptibility to infection, but also reducing the infectiousness of breakthrough infections in vaccinated cases. To disentangle the vaccine effectiveness against susceptibility to infection ( V E S ) and vaccine effectiveness against infectiousness ( V E I ), we took advantage of Danish national data comprising 24,693 households with a primary case of SARS-CoV-2 infection (Delta Variant of Concern, 2021) including 53,584 household contacts. In this setting, we estimated V E S as 61% (95%-CI: 59-63), when the primary case was unvaccinated, and V E I as 31% (95%-CI: 26-36), when the household contact was unvaccinated. Furthermore, unvaccinated secondary cases with an infection exhibited a three-fold higher viral load compared to fully vaccinated secondary cases with a breakthrough infection. Our results demonstrate that vaccinations reduce susceptibility to infection as well as infectiousness, which should be considered by policy makers when seeking to understand the public health impact of vaccination against transmission of SARS-CoV-2.

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  1. Version published to 10.1038/s41467-022-31494-y
  2. ScreenIT

    SciScore for 10.1101/2022.01.06.22268841: (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

    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:
    Some limitations apply to this study. Firstly, we did not have access to clinical information. Secondly, vaccination status may affect the behavior of both primary cases and potential secondary cases, as they may adhere less to non-pharmaceutical interventions (NPIs) once they or others are vaccinated. Thus, the estimates in our study reflect both the biological aspect of susceptibility and transmissibility, as well as the behavioral aspects, and does not confer any information regarding severity of illness, which is expected to be lower among vaccinated individuals. There are several behavioral aspects relating to vaccination. Once a primary case is identified within the household, the other members might allocate their time with that individual, conditional on their own vaccination status. For example, if the primary case is a child and one parent is fully vaccinated, while the other is not, then the family may choose to allocate the majority of childcare during the infection to the vaccinated parent, as they have a lower risk of being infected. This changed contact pattern may lead to a higher rate of infections in vaccinated individuals in households where there are also unvaccinated members. Furthermore, vaccinated individuals may in general adhere less to non-pharmaceutical interventions, such as keeping distance, wearing masks, etc. due to a perceived lower susceptibility and transmissibility. Unvaccinated individuals may be identified earlier in their infection than v...

    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

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  3. Version published to 10.1101/2022.01.06.22268841v1 on medRxiv