Transmission of SARS-CoV-2 following exposure in school settings: experience from two Helsinki area exposure incidents.

Abstract

Background: The role of children in SARS-CoV-2 transmission is unclear. We investigated two COVID-19 school exposure incidents in the Helsinki area. Methods: We conducted two retrospective cohort studies after schools exposures, with a household transmission extension. We defined a case as an exposed person with either a positive RT-PCR, or positive microneutralisation testing (MNT) as confirmation of SARS-CoV-2 nucleoprotein IgG antibodies detection via fluorescent microsphere immunoassay (FMIA). We recruited close school contacts and families of school cases, calculated attack rates (AR) on school level and families, and identified transmission chains. Findings: In incident A, the index was a pupil. Participation rate was 74% (89/121), and no cases were identified. In incident B, the index was a member of school personnel. Participation rate was 81% (51/63). AR was 16% (8/51): 6 pupils and 1 member of school personnel were MNT and FMIA positive; 1 pupil had a positive RT-PCR, but negative serology samples. We visited all school cases' families (n=8). The AR among close household contacts was 42% (9/20 in 3/8 families) but other plausible sources were always reported. At three months post-exposure, 6/8 school cases were re-sampled and still MNT positive. Interpretation: When the index was a child, no school transmission was identified, while the occurrence of an adult case led to a 16% AR. Further cases were evidenced in 3 families, but other transmission chains were plausible. It is likely that transmission from children to adults is limited. Funding: The Finnish Institute for Health and Welfare funded this study.

Retrospective assessment of SARS-COV2 circulation in two hospital nurseries hosting healthcare workers’ children during lockdown in one of the most affected French areas

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Intra-Household and Close-Contact SARS-CoV-2 Transmission Among Children – a Systematic Review

“…Dub et al (31) from Finland performed a retrospective study after two school outbreaks of SARS-CoV-2 with one infected adult and one infected child respectively. For the adult index case, neutralizing IgG-antibodies for SARS-CoV-2 were identified in 17% of exposed students (7 of 42) and 11% of exposed adults (1 of 9).…”

To What Extent Does In-Person Schooling Contribute to the Spread of COVID-19? Evidence from Michigan and Washington

“…The handful of studies that have examined whether COVID infections in schools appear to spread within and outside of the school reach mixed conclusions. Two retrospective case studies-one in three schools in northern France and one in two Helsinki area schools-find that infected students did not appear to spread COVID beyond the school setting (Dub et al, 2020;Fontanet et al, 2020). A study of children who were infected with the virus in Mississippi finds students performed similarly in reading in fall 2020 as their counterparts in fall 2019, while math achievement was 5-10 percentile points lower for these students.…”