High Infection Secondary Attack Rates of Severe Acute Respiratory Syndrome Coronavirus 2 in Dutch Households Revealed by Dense Sampling

  1. Daphne F M Reukers
  2. Michiel van Boven
  3. Adam Meijer
  4. Nynke Rots
  5. Chantal Reusken
  6. Inge Roof
  7. Arianne B van Gageldonk-Lafeber
  8. Wim van der Hoek
  9. Susan van den Hof

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Abstract

Background

Indoor environments are considered one of the main settings for transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Households in particular represent a close-contact environment with high probability of transmission between persons of different ages and roles in society.

Methods

Households with a laboratory-confirmed SARS-CoV-2 positive case in the Netherlands (March-May 2020) were included. At least 3 home visits were performed during 4-6 weeks of follow-up, collecting naso- and oropharyngeal swabs, oral fluid, feces and blood samples from all household members for molecular and serological analyses. Symptoms were recorded from 2 weeks before the first visit through to the final visit. Infection secondary attack rates (SAR) were estimated with logistic regression. A transmission model was used to assess household transmission routes.

Results

A total of 55 households with 187 household contacts were included. In 17 households no transmission took place; in 11 households all persons were infected. Estimated infection SARs were high, ranging from 35% (95% confidence interval [CI], 24%-46%) in children to 51% (95% CI, 39%-63%) in adults. Estimated transmission rates in the household were high, with reduced susceptibility of children compared with adolescents and adults (0.67; 95% CI, .40-1.1).

Conclusion

Estimated infection SARs were higher than reported in earlier household studies, presumably owing to our dense sampling protocol. Children were shown to be less susceptible than adults, but the estimated infection SAR in children was still high. Our results reinforce the role of households as one of the main multipliers of SARS-CoV-2 infection in the population.

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  1. Version published to 10.1093/cid/ciab237
  2. ScreenIT

    SciScore for 10.1101/2021.01.26.21250512: (What is this?)

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

    Table 1: Rigor

    Institutional Review Board StatementIRB: The generic and adapted study protocols were approved by the Medical-Ethical Review Committee of the University Medical Center Utrecht (NL13529.041.06).
    Consent: Data collection: Two research nurses performed the first home visit within 24 hours after inclusion to collect the informed consent forms and the first samples from all participants (see Table 1 for schedule of sample collection).
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: Thank you for sharing your code.

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    We discuss two related limitations of our analyses. For inclusion of households our study depended on the prevailing testing policies and infected population in difference age groups. This may well have resulted in a high likelihood of selecting (symptomatic) adult index cases, such that index cases may not be representative of infections in the population. Standard practice for estimating SAR partly solves this problem by taking into account all secondary infections in the household while leaving the index case out from the analyses [20]. Related to this is the fact that the index case may not always be the primary (i.e. first) case in the household [19, 20], such that standard estimates of SARs may not be indicative of transmission routes in the household. A previous household study tried to solve this issue by including index cases and excluding primary cases [37], but this introduces bias as it would artificially increase the SAR of the prevailing type of the index cases (i.e. adults). In a sensitivity analysis, we reran the analyses using logistic regression by excluding both the primary and index case, and found relatively small impact on the estimated SARs in different age groups (not shown). The transmission model analyses do not suffer from these problems, but they do require that the primary case in the household can be identified, and this is often not possible in retrospective household analyses.

    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 10.1101/2021.01.26.21250512v1 on medRxiv