Children and COVID-19: is it safe to return to school?

Much has been made of the UK government’s plans to reopen schools in June although there has been much concern expressed by parents and some local authorities that this move is far too soon.

The intention to open schools is based on the premise that children are unlikely to pass on the virus to either other children or adults but how robust is the evidence used to support this claim?

There has been a great deal of research on this topic that has been quickly published online though most of it has not been subject to peer review. One review of the preliminary evidence suggested that children were just as likely as adults to become infected with COVID-19 but also that children less liable to be symptomatic or to develop severe symptoms.1 In an analysis of just over 2000 Chinese children (median age 7 years) infected with COVID-19 during the early stages of the pandemic, it was found that 94% were either asymptomatic or had mild to moderate symptoms although the authors concluded that children of all ages were susceptible to the virus.2 The fact that mortality is considerably less in children in borne out by the latest Office for National Statistics (ONS) report which showed that up to the 8 May, of the 37,375 COVID-19 recorded deaths in the UK, only three have occurred in those between the ages of 1 and 14.3 Furthermore, in a community testing study in Vo, Italy (which has not been subject to peer review) in which nasopharyngeal swabs were collected from between 71 and 86% of the eligible population in all age groups, no infections were found in children aged between 0 and 10 years, despite the fact that they lived in the same house as infected people.4 Despite this, the latest data from the ONS infection survey observed no difference in the proportion testing positive between age categories.5 For instance, the report shows that 0.26% of those in the age category 2–11 tested positive, compared with 0.32% in those aged 70 years and over.

The ONS data provides valuable insight of the positivity rate but says nothing about the prevalence rate, that is, the number of people who actually develop COVID-19 symptoms. Some understanding of the prevalence rate can be determined by examining what researchers term the “attack rate”, in other words, the proportion of people who become infected after contact with someone has tested positive. One Chinese study assessed 1286 contacts of 391 index cases (that is, those who had tested positive) and found that the attack rate was 7.4% in children under 10 years of age compared to the population average of 6.6%.6 In another Chinese study, the observed attack rate in children was 5.26% which was considerably lower than the rate of 17.69% in those aged 60 years and over.7 Finally, in a review of Chinese contract tracing surveys it was found that the odds ratio for infection in those aged 0–14 years was 0.34 (95% CI 0.24 –0.49) compared to an odds ratio of 1.47 (95% CI 1.12–1.92) in those aged 65 years and over.8

Whilst the above information indicates that children can become infected, a much more relevant question, especially in relation to the reopening of schools, is how easy is it for infected children to pass on the virus? Unfortunately, this is a much more difficult question to answer, although emerging evidence does offer some hope that transmission of the virus from children is less likely. In a report from New South Wales, Australia, it was found that in a total of six confirmed infections (one child and five staff), there were a total of 168 contacts of which only one individual became infected. The report also concluded that the authors found no evidence of children infecting teachers.9 Further reassurance that transmission from children is improbable comes from a French study in which a child to tested positive for COVID-19 did not transmit the virus to anyone else despite their interaction with a large number of contacts.10

In summary, it appears that although children can contract the virus just as easily as adults, the severity of the illness is much less. In addition, while the available data is limited, it does seem that infected children are less liable to pass on COVID-19 and this should offer some reassurance to parents who are concerned about sending their offspring back to school in the near future.

References

1. Zimmermann P, Curtis N. Coronavirus infection in children. Pediatr Infect Dis J 2020;39:355-68.
2. Dong Y et al. Epidemiology of COVID-19 among children in China. Pediatrics 2020; Apr 2020.
3. Office for National Statistics. Deaths involving COVID-19 up to 8 May.
   www.ons.gov.uk/peoplepopulationandcommunity/healthandsocialcare/conditionsanddiseases/articles/coronaviruscovid19roundup/2020-03-26#coviddeaths (accessed May 2020).
4. Lavezzo E et al. Suppression of COVID-19 outbreak in the municipality of Vo, Italy. MedRxiv 2020 https://doi.org/10.1101/2020.04.17.20053157
5. Office for National Statistics. Coronavirus (COVID-19) Infection survey pilot: England, 21 May 2020.
   www.ons.gov.uk/peoplepopulationandcommunity/healthandsocialcare/conditionsanddiseases/bulletins/coronaviruscovid19infectionsurveypilot/england21may2020 (accessed May 2020).
6. Bi Q et al. Epidemiology and transmission of COVID-19 in 391 cases and 1286 of their close contacts in Shenzhen, China: a retrospective cohort study. Lancet infect Dis 2020;Apr 27;S1473.
7. Jing Q et al. Household secondary attack rate of COVID-19 and associated determinants. MedRxiv 2020; Apr 15: doi: 10.1101/2020.04.11.20056010.
8. Zhaung J, Litvinova M, Liang Y et al. Changes in contact patterns shape the dynamics of the COVID-19 outbreak in China. Science 2020 Apr 29. Eabb8001.
9. NCIRS. COVID-19 in schools – the experience in NSW. http://ncirs.org.au/sites/default/files/2020-04/NCIRS%20NSW%20Schools%20COVID_Summary_FINAL%20public_26%20April%202020.pdf (accessed May 2020).
10. Danis K et al. Cluster of coronavirus disease 2019 (COVID-19) in the French Alps. Clin Infect Dis 2020; Apr 11: doi: 10.1093/cid/ciaa424.