Epidemiological, virological and serological investigation of a SARS-CoV-2 outbreak (Alpha variant) in a primary school: A prospective longitudinal study

  1. Elsa Lorthe
  2. Mathilde Bellon
  3. Grégoire Michielin
  4. Julie Berthelot
  5. María-Eugenia Zaballa
  6. Francesco Pennacchio
  7. Meriem Bekliz
  8. Florian Laubscher
  9. Fatemeh Arefi
  10. Javier Perez-Saez
  11. Andrew S. Azman
  12. Arnaud G. L’Huillier
  13. Klara M. Posfay-Barbe
  14. Laurent Kaiser
  15. Idris Guessous
  16. Sebastian J. Maerkl
  17. Isabella Eckerle
  18. Silvia Stringhini
  19. on behalf of the SEROCoV-Schools Study Group

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Abstract

To report a prospective epidemiological, virological and serological investigation of a SARS-CoV-2 outbreak in a primary school.

Methods

As part of a longitudinal, prospective, school-based surveillance study, this investigation involved repeated testing of 73 pupils, 9 teachers, 13 non-teaching staff and 26 household members of participants who tested positive, with rapid antigen tests and/or RT-PCR (Day 0–2 and Day 5–7), serologies on dried capillary blood samples (Day 0–2 and Day 30), contact tracing interviews and SARS-CoV-2 whole genome sequencing.

Results

We identified 20 children (aged 4 to 6 years from 4 school classes), 2 teachers and a total of 4 household members who were infected by the Alpha variant during this outbreak. Infection attack rates were between 11.8 and 62.0% among pupils from the 4 school classes, 22.2% among teachers and 0% among non-teaching staff. Secondary attack rate among household members was 15.4%. Symptoms were reported by 63% of infected children, 100% of teachers and 50% of household members. All analysed sequences but one showed 100% identity. Serological tests detected 8 seroconversions unidentified by SARS-CoV-2 virological tests.

Conclusions

This study confirmed child-to-child and child-to-adult SARS-CoV-2 transmission and introduction into households. Effective measures to limit transmission in schools have the potential to reduce the overall community circulation.

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  1. Version published to 10.1371/journal.pone.0272663
  2. Version published to 10.1101/2021.10.26.21265509v2 on medRxiv
  3. ScreenIT

    SciScore for 10.1101/2021.10.26.21265509: (What is this?)

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

    Table 1: Rigor

    EthicsField Sample Permit: We collected capillary blood on a Neoteryx Mitra® collection device, and tested for anti-Spike-SARS-CoV-2 IgG on a microfluidic nanoimmunoassay as described previously [15].
    IRB: Ethics: This study was approved by the ethics committee of the Canton of Geneva (Project ID 2020-02957).
    Consent: All parents and teachers were informed about the study and gave written consent while children gave verbal consent to participate.
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Cell Line AuthenticationAuthentication: We used the Panbio COVID-19 Ag rapid test (Abbott) which has been validated in adults for use with oropharyngeal instead of nasopharyngeal swabs [16].

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    We used the Panbio COVID-19 Ag rapid test (Abbott) which has been validated in adults for use with oropharyngeal instead of nasopharyngeal swabs [16].
    Abbott
    suggested: (Abbott, RRID:SCR_010477)

    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 limitations: Few large SARS-CoV-2 outbreaks in young children in school settings have been documented so far [31,32], even fewer involved an investigation of variants of concern. As part of an ongoing prospective study, this investigation started less than 24 hours after the first case was laboratory-confirmed and involved the use of three complementary approaches. We followed up and repeatedly tested all contacts within four classes regardless of symptoms. Repeated serological tests proved useful to retrieve seroconversions following asymptomatic or undiagnosed infections. However, we relied on a limited number of cases. Not all children and adults were tested, which could lead to underestimating IAR and SAR. We might have missed infections among adults who were vaccinated between D0-2 and D30, as we could not distinguish between antibodies due to vaccination and those due to infection. Also, we could not test the household members of cases only detected by seroconversion at D30 with no positive RT-PCR/RDT, leading to a potential underestimation of secondary attack rates. The study was performed before the circulation of the more infectious Delta variant; estimates are therefore likely to be underestimated in a context of Delta dominance [33].

    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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  4. Version published to 10.1101/2021.10.26.21265509v1 on medRxiv