Study: COVID19 Infection & Transmission in 5-13 year olds ‘minimal’

Written by Eurosurveillance on January 30, 2021. Posted in Current News

Study in Norway tested all contacts of 5 to 13 year olds with covid. They conclude “transmission of SARS-CoV-2 from children under 14 years of age was minimal in primary schools in Oslo and Viken, the 2 counties with the highest COVID-19 incidence”

Below we have select extracts from the new study ‘Minimal transmission of SARS-CoV-2 from paediatric COVID-19 cases in primary schools, Norway, August to November 2020,’ [1]

Since summer 2020, a considerable increase in coronavirus disease (COVID-19) infections has been reported across Europe [1], including in Norway [2]. A better understanding of children’s role in transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in school settings is urgently needed. Although several studies have reported limited transmission of SARS-CoV-2 among children in school settings [3–7], few have comprised systematic testing of contacts, including asymptomatic contacts. We aimed to examine transmission of SARS-CoV-2 from confirmed paediatric COVID-19 cases in primary schools in Norway by systematically testing all contacts within the school twice during their quarantine period.

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Oslo and Viken were the counties in Norway with the highest 14-day incidence of COVID-19, ranging from 19.3 to 94.9 cases per 100,000 inhabitants in weeks 36 to 46 2020 [2]. During our observation period, from 28 August 2020 to 11 November 2020, the number of confirmed cases increased in these counties, including among children 5–13 years old (Figure 1).

Figure 1.Laboratory-confirmed COVID-19 cases by date of sampling and age, Oslo and Viken counties, Norway, 28 August–11 November 2020 (n = 9,416)

COVID-19: coronavirus disease.

Source: Norwegian Surveillance System for Communicable Diseases (MSIS).

An index case was defined as a case aged 5–13 years in Oslo or Viken county with PCR-confirmed SARS-CoV-2 infection, who had attended school within 48 hours before symptom onset or date of sampling. We prospectively included contact tracings around 13 index cases. For each index case, public health officials identified exposed child and adult school contacts (Figure 2). All consenting cases and contacts delivered two self-collected saliva samples; the first was collected as soon as possible after they were identified, and the second was collected at the end of their 10-day quarantine period (Figure 2). We excluded contact tracings with adult COVID-19 index cases.

Figure 2.Overview of included COVID-19 contact tracings in schools, Oslo and Viken counties, Norway, 28 August–11 November 2020 (n = 13)

^a Schools were closed due to autumn break in week 40 (28 September–2 October 2020).

^b The first saliva samples were taken from the index case twice, with 3 days between the two; the second of these was positive. There were 6 days between the original nasopharyngeal sample and the first positive saliva sample. The third and last saliva sample was taken at the end of the case’s 10-day quarantine.

^c One or two primary cases (school contacts who tested positive for SARS-CoV-2 in the first saliva sample) were detected in the contact tracing.

A primary case was defined as a school contact who tested positive for SARS-CoV-2 in the first saliva sample. A secondary case was defined as a school contact who tested positive for SARS-CoV-2 in the second saliva sample, following a first negative test.

Study invitations were sent to adult contacts (staff) and parents of child contacts through the school’s digital communication platform. We distributed equipment and detailed instructions for self-collection of two saliva samples to consenting participants on the same day. The first saliva sample was taken the following morning before eating, drinking or brushing teeth; the second saliva sample was taken at the end of the quarantine period with the same instructions (Figure 2). The participants added viral transport media to the saliva sample. Each saliva sample was analysed for SARS-CoV-2 using PCR (RdRp gene) [8] at the National Reference Laboratory of influenza and coronaviruses with outbreak potential (including SARS-CoV-2) at the Department of Virology at the Norwegian Institute of Public Health in Oslo.

Minimal transmission of SARS-CoV-2 in primary schools

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Thirteen contact tracings from primary schools were included: eight in the age group 5–10 years old (grades 1–4) and five in the age group 11–13 years old (grades 5–7) (Figure 2). A total of 13 index cases and 292 school contacts participated in the study. In Contact Tracing 7, the index case did not consent to participate and saliva samples from this individual could not be collected. In Contact Tracing 8, two index cases were included, and in all the remaining 11 contact tracings one index case was included. Four of the 13 index cases had attended school with mild symptoms (in Contact Tracings 2, 3, 4 and 13); however, among these four index cases’ contacts, only two primary cases (both in Contact Tracing 13) and no secondary case was identified. The remaining index cases were asymptomatic while attending school. All index cases, except one, had household members who were diagnosed with COVID-19 before the index cases themselves tested positive.

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Conclusions

Systematic tracing and testing of school contacts of paediatric COVID-19 cases showed minimal child-to-child and child-to-adult transmission in primary schools with implemented IPC measures. The results obtained during low to medium community transmission demonstrate the limited role of children in transmission of SARS-CoV-2 in school settings. This is an important finding in view of the ongoing discussions on school closures and use of quarantine for a large number of children. Strengthening of IPC measures in schools when community transmission levels increase could be an option.

[1] Brandal Lin T, Ofitserova Trine S, Meijerink Hinta, Rykkvin Rikard, Lund Hilde M, Hungnes Olav, Greve-Isdahl Margrethe, Bragstad Karoline, Nygård Karin, Winje Brita A. Minimal transmission of SARS-CoV-2 from paediatric COVID-19 cases in primary schools, Norway, August to November 2020. Euro Surveill. 2021;26(1):pii=2002011. https://doi.org/10.2807/1560-7917.ES.2020.26.1.2002011

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