Transmission dynamics of COVID-19 in household and community settings in the United Kingdom, January to March 2020

  1. Jamie Lopez Bernal
  2. Nikolaos Panagiotopoulos
  3. Chloe Byers
  4. Tatiana Garcia Vilaplana
  5. Nicki Boddington
  6. Xu-Sheng Zhang
  7. Andre Charlett
  8. Suzanne Elgohari
  9. Laura Coughlan
  10. Rosie Whillock
  11. Sophie Logan
  12. Hikaru Bolt
  13. Mary Sinnathamby
  14. Louise Letley
  15. Pauline MacDonald
  16. Roberto Vivancos
  17. Obaghe Edeghere
  18. Charlotte Anderson
  19. Karthik Paranthaman
  20. Simon Cottrell
  21. Jim McMenamin
  22. Maria Zambon
  23. Gavin Dabrera
  24. Mary Ramsay
  25. Vanessa Saliba

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Abstract

Households appear to be the highest risk setting for COVID-19 transmission. Large household transmission studies in the early stages of the pandemic in Asia reported secondary attack rates ranging from 5 to 30%.

Aim

We aimed to investigate the transmission dynamics of COVID-19 in household and community settings in the UK.

Methods

A prospective case-ascertained study design based on the World Health Organization FFX protocol was undertaken in the UK following the detection of the first case in late January 2020. Household contacts of cases were followed using enhanced surveillance forms to establish whether they developed symptoms of COVID-19, became confirmed cases and their outcomes. We estimated household secondary attack rates (SAR), serial intervals and individual and household basic reproduction numbers. The incubation period was estimated using known point source exposures that resulted in secondary cases.

Results

We included 233 households with two or more people with 472 contacts. The overall household SAR was 37% (95% CI: 31–43%) with a mean serial interval of 4.67 days, an R 0 of 1.85 and a household reproduction number of 2.33. SAR were lower in larger households and highest when the primary case was younger than 18 years. We estimated a mean incubation period of around 4.5 days.

Conclusions

Rates of COVID-19 household transmission were high in the UK for ages above and under 18 years, emphasising the need for preventative measures in this setting. This study highlights the importance of the FFX protocol in providing early insights on transmission dynamics.

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  1. Version published to 10.2807/1560-7917.es.2022.27.15.2001551
  2. ScreenIT

    SciScore for 10.1101/2020.08.19.20177188: (What is this?)

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

    Table 1: Rigor

    Institutional Review Board Statementnot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot 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:
    The study also has a number of limitations: test results were not available for some participants who developed symptoms, therefore we likely under-ascertained confirmed secondary cases. Furthermore, as with previous studies, testing was focussed on those who develop symptoms. Estimates of asymptomatic infection range from 4% to 41%, therefore we are likely to have missed asymptomatic cases (32). Furthermore, rates of asymptomatic infection appear to be highest in children, therefore we particularly underestimate secondary infection rates in children (29, 32). We are currently undertaking further analyses of household transmission incorporating swabbing of asymptomatics and serology which will provide a better understanding of true secondary infection rates and asymptomatic infection. We are also limited in our ability to draw any clear conclusions about transmission from children due to the small number of households with a child as a primary case. Since the early stages of the pandemic, data from the FF100 study has been shared in real-time with independent modelling groups advising government and has informed policy making and public health management guidance. The high household SAR and the lack of transmission in a range of other settings highlight the importance of the household setting for onwards transmission. This emphasises the need for hygiene measures within the household and, where there are vulnerable members of the household, maintaining distancing within the h...

    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.

    About SciScore

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  3. Version published to 10.1101/2020.08.19.20177188 on medRxiv