Covid and Kids: The Evidence.

Population share and contribution to covid infections per age group in the US (Monod, Science, March 2021)

Update: March 2021
Share on: Twitter / Facebook

A brief overview of the current scientific evidence regarding covid-19, children and schools.

1. Summary

  1. Covid in children remains mostly asymptomatic (about 40% of all cases) or mild.
  2. Both the risk of infection and the risk of transmission are significantly lower in children, but not in adolescents, compared to adults. Infection risk increases linearly with age from 10 to 20 years.
  3. Both children and adults get infected mostly by adults and adolescents, not by children.
  4. Transmission in school settings is low, even without masks, especially if symptomatic children stay at home. Teachers are not at higher risk of infection than people in other occupations.
  5. In contrast to influenza, children and schools are not major ‘drivers’ of the coronavirus pandemic, and school closures have had a very limited impact on overall infections.
  6. Among symptomatic children, up to 10% experience prolonged symptoms or fatigue lasting several weeks or months (i.e. post-acute covid or post-viral fatigue).
  7. Covid-related multisystem inflammatory syndrome in children (MIS-C) is a serious but rare condition, affecting between 1 in 5000 and 1 in 50,000 children (i.e. less than 0.02%).
  8. The cell receptors used by the novel coronavirus are regulated by sexual hormones and their expression is therefore age-dependent and significantly lower in children below 12. The new coronavirus variants (N501Y.V1-3) do not preferentially infect children, either.
  9. Studies and media reports claiming children and schools are major ‘drivers’ of the pandemic often don’t distinguish between school closures and other measures, or between children and adolescents, or between children infecting adults and adults infecting children.
  10. Nevertheless, cases of transmission at school and of children infecting their parents do occur regularly. Teachers and parents at risk should consider prophylactic treatment options.
  11. Many states and countries could drive down coronavirus infections without closing elementary schools, e.g. Florida, France, Iceland, Ireland, Japan, Sweden and Switzerland, among others.
  12. The social, psychological, educational and in some cases even physical impact of lockdowns and other restrictions is generally most severe in children and adolescents.

2. Studies

For a comprehensive overview of pediatric covid studies see the DFTB portal.

  1. Immune response: “The kids lacked nucleocapsid-specific antibodies, which suggests that they aren’t experiencing widespread infection. Children’s immune responses seem to be able to eliminate the virus before it replicates in large numbers.” (Nogrady, Nature, December 2020)
  2. Household transmission: “Children are unlikely to cause household COVID-19 clusters or be major drivers of the pandemic even if attending school. Interventions aimed at children are expected to have a small impact on reducing SARS-CoV-2 transmission.” (Soriano-Arandes, Clinical Infectious Diseases, March 2021)
  3. Deaths: “In the USA, UK, Italy, Germany, Spain, France, and South Korea, deaths from COVID-19 in children remained rare up to February 2021, at 0.19 per 100 000 population, comprising 0.54% of the estimated total mortality from all causes in a normal year.” (Bhopal, The Lancet Child and Adolescent Health, March 2021)
  4. Austria: “In school children, the infection rate with SARS‐CoV‐2 is low and associated with a mild or asymptomatic course of disease. Virus spreading seemed to occur more likely in intergenerational contacts than among siblings in the same household. () Virus spreading from child-to-child in the same household seems to occur rarely.” (Szepfalusi, PAI, January 2021)
  5. Germany 1: “Only few and mostly small COVID-19 school outbreaks had been reported in Germany overall, suggesting that the containment measures are sufficient to reduce spillover into the community.” (Kampe, Eurosurveillance, September 2020)
  6. Germany 2: “Our investigation suggests that child-to-child transmission in schools and childcare facilities is uncommon and not the primary cause of SARS-CoV-2 infection in children.” (Ehrhardt, Eurosurveillance, September 2020)
  7. Iceland: “This 40,000-person study found that children under 15 were about half as likely as adults to be infected, and only half as likely as adults to transmit the virus to others. Almost all the coronavirus transmissions to children came from adults. But if children are poor catchers and slight spreaders, schools should simply mirror what’s happening in the wider community.” (Parshley, NG, December 2020)
  8. Ireland: “No evidence of secondary transmission of COVID-19 from children attending school in Ireland, 2020. () In summary, examination of all Irish paediatric cases of COVID-19 attending school during the pre-symptomatic and symptomatic periods of infection (n = 3) identified no cases of onward transmission to other children or adults within the school and a variety of other settings.” (Heavey, Eurosurveillance, May 2020)
  9. Israel 1: “This analysis does not support a major role of school reopening in the resurgence of the COVID-19 curve in Israel. Easing restrictions on large scale gatherings was the major influence on this resurgence.” (Somekh, CID, January 2021)
  10. Israel 2: “We estimate that the susceptibility of children (under 20 years old) is 43% of the susceptibility of adults. The infectivity of children was estimated to be 63% relative to that of adults.” (Dattner, Medxriv, October 2020)
  11. Italy: “Our analysis does not support a role for school opening as a driver of the second wave of SARS-CoV-2 epidemics in Italy, a large European country with high SARS-CoV-2 incidence.” (Gandini, Medrxiv, January 2021)
  12. Korea: “Korea had a successful transition from school closure to online and off-line school opening, which did not cause significant school-related outbreak among the pediatric population.” (Yoon, YKMS, November 2020)
  13. Norway: “This prospective study shows that transmission of SARS-CoV-2 from children under 14 years of age was minimal in primary schools in Oslo and Viken, the two Norwegian counties with the highest COVID-19 incidence () symptomatic children were asked to stay home from school () Use of face masks is not recommended in schools in Norway.” (Brandal, Eurosurveillance, January 2021)
  14. Sweden/Finland: “There was no measurable difference in the number of coronavirus cases among children in Sweden, where schools were left open, compared with neighboring Finland, where schools were shut, according to the findings.” (PHAS, July 2020)
  15. Switzerland: “In a setting of high incidence of SARS-CoV-2 infections, unrecognized virus spread within schools was very low. Schools appear to be safe with the protective measures in place (e.g., clearly symptomatic children have to stay at home, prompt contact tracing with individual and class-level quarantine, and structured infection prevention measures in school).” (Kriemler, Medrxiv, December 2020)
  16. UK 1 (families): “Among 9,157,814 adults ≀65 years, living with children 0-11 years was not associated with increased risks of recorded SARS-CoV-2 infection, COVID-19 related hospital or ICU admission but was associated with reduced risk of COVID-19 death. Living with children aged 12-18 years was associated with a small increased risk of recorded SARS-CoV-2 infection, but not associated with other COVID-19 outcomes. () Among 2,567,671 adults >65 years there was no association between living with children and outcomes related to SARS-CoV-2. We observed no consistent changes in risk following school closure.” (Forbes, Medxriv, November 2020)
  17. UK 2 (families): “Increased household exposure to young children was associated with an attenuated risk [!] of testing positive for SARS-CoV-2 and appeared to also be associated with an attenuated risk of COVID-19 disease severe enough to require hospitalisation.” (Wood, Medxriv, September 2020)
  18. USA (Wisconsin): “Among 191 cases identified in students and staff members, only seven (3.7%) cases, all among students, were linked to in-school spread. () Despite widespread community transmission, COVID-19 incidence in schools conducting in-person instruction was 37% lower than that in the surrounding community.” (CDC, MMWR, January 2021)
  19. USA (North Carolina): “In the first 9 weeks of in-person instruction in North Carolina schools, we found extremely limited within-school secondary transmission of SARS-CoV-2, determined by contact tracing.” (Zimmermann, Pediatrics, January 2021)
  20. USA (child care programs): “Within the context of considerable infection mitigation efforts in US child care programs, exposure to child care during the early months of the US pandemic was not associated with an elevated risk for COVID-19 transmission to providers.” (Gilliam, Pediatrics, January 2021)
  21. USA (Michigan; families): “In all cases where a household sick contact was identified, there was no evidence of child-to-adult transmission, and only one case of child-to-child transmission. A parent was the most common index household sick contact. () This is consistent with other studies that suggest that children are not the primary vectors for SARS-CoV-2 infection as was initially suspected; rather children are most commonly infected by adult sick contacts.” (Pitman-Hunt, PIDS, November 2020)
  22. ECDC: “Children of all ages are susceptible to and can transmit SARS-CoV-2. Younger children appear to be less susceptible to infection, and when infected, less often lead to onward transmission than older children and adults. () Transmission of SARS-CoV-2 can occur within school settings and clusters have been reported in preschools, primary and secondary schools. Incidence of COVID-19 in school settings appear to be impacted by levels of community transmission. Where epidemiological investigation has occurred, transmission in schools has accounted for a minority of all COVID-19 cases in each country.” (ECDC, December 2020)

3. Explanation of contrary evidence

Studies apparently showing that children and schools play a major role in the covid pandemic often didn’t distinguish between children and adolescents, or between schools and universities, or between school closures and other concurrent measures, or between children infecting adults and adults infecting children. Nevertheless, it is clear that even children do contribute to the pandemic.

  1. Schools: A much-cited modelling study published in Nature Human Behaviour in November 2020 on the effectiveness of worldwide covid-19 government interventions appeared to show that ‘school closures’ were the second most effective measure, but the study did not distinguish between schools and universities, treating both as ‘educational settings’.
  2. India: A large Indian study published in Science appeared to show that children transmit the coronavirus as often as adults, but the study did not properly identify index cases and considered primarily symptomatic children, not children in general.
  3. South Korea: A study from South Korea appeared to show that children and adolescents aged 10 to 19 years were just as infectious as adults, but the study did not consider shared exposure to other adults, which fully explained the apparent effect.
  4. UK: A British government report appeared to show that children and adolescents have lower susceptibility but much higher transmissibility, but other large studies could not confirm this.
  5. Israel: A well-known case study described an outbreak in an Israeli high school in May 2020. But a later and more comprehensive study found “no major role of school reopening in the resurgence of the COVID-19 curve in Israel”.
  6. USA: A US study described virus transmission in three child care facilities. But a later study found that “exposure to child care during the early months of the US pandemic was not associated with an elevated risk for COVID-19 transmission to providers.”

See also

Share on: Twitter / Facebook

Up ↑