SARS CoV2 transmission in children

A collection of links on SARS CoV2 transmission in children.

Update 2020/03/18: tweet with mask data in Florida schools:

There’s this which summarizes some findings:

Of 39 evaluable households, in only 3 (8%) was a child the suspected index case

…Of 68 children with confirmed COVID-19 … 65 (95.59%) patients were HHCs of previously infected adults.7 Of 10 children hospitalized … in only 1 was there possible child to adult transmission

…a 9-year-old boy with respiratory symptoms associated with picornavirus, influenza A, and SARS-CoV-2 coinfection was found to have exposed over 80 classmates at 3 schools; no secondary contacts became infected, despite numerous influenza infections within the schools, suggesting an environment conducive to respiratory virus transmission

…In New South Wales, Australia, 9 students and 9 staff infected with SARS-CoV-2 across 15 schools had close contact with a total of 735 students and 128 staff. Only 2 secondary infections were identified, none in adult staff; 1 student in primary school was potentially infected by a staff member, and 1 student in high school was potentially infected via exposure to 2 infected schoolmates.

This from Ireland is a case study with just 6 infected kids who attended school while infected and they infected zero additional people in school (I’d love this same study but with 500 infected kids who then went to school, but all we get is n=6):

This has more small studies summarized, some overlap with the first one. They all find that children are the “index case” in a very small number of cases (like 5%):

Also this piece in NPR which finds:

There are almost no recorded cases of child-to-adult transmission of COVID-19

This from a Spanish study covering more than 1,900 people:

we were able to detect 39 newly appeared index cases … of which 30 were found in children …. These children had 253 contacts, who were boys and girls from their respective cohabitation groups. From these, there were only 12 contagions, which is 4.7% and an R reproduction rate of 0.3. This is a low R number, six times lower than the one that we have found among the general population, which ranges from 1.7 to 2

Update 2020/09/10: a summary by Nic Lewis of an EU CDC report of the transmission of SARS CoV2 in schools finds that across Europe – where schools were more likely to remain open than in the US – there was little to no transmission taking place in schools, either from student to student or student to staff. :

The conclusion from these investigations is that child-to-child transmission in schools is uncommon and not the primary cause of SARS-CoV-2 infection of children …

Where COVID-19 in children was detected and contacts followed-up, no adult contacts in the school setting have been detected as SARS-CoV-2 positive during the follow-up period. The conclusion from these investigations is that children are not the primary drivers of SARS-CoV-2 transmission to adults in the school setting.

Update 2021/01/28: Wisconsin study from cdc. Despite “widespread community transmission”, “COVID-19 case rates among students and staff members were lower (191 cases among 5,530 persons, or 3,453 cases per 100,000) than were those in the county overall (5,466 per 100,000).” And more critically, of the 191 cases among students and staff, “only seven (3.7%) were associated with in-school transmission, all in students.” “No infections among staff members were found to have been acquired at school.”

Update 2021/01/28: WHO working group. “Data suggest that children and adolescents are followers, not drivers, of the pandemic, with a slower dynamic in younger children.” [p.4]. “Schools should be the last place to close [since] school closures are detrimental to child mental health and well-being and education outcomes.” [p.5]

Update 2021/01/30: study from Norway where masks are not worn in school and asymptomatic children were tested. Low in school infections among students and staff.

Update 2021/01/31: this tweet links to a study showing that schools opening in Germany in the fall coincided with reduced covid spread:

Update 2021/02/10: this study of Scottish schools:

the relative risk in teachers (among 18,479 cases and controls) for hospitalisation was rate ratio (RR) 0.97 (95%CI 0.72-1.29) and for severe COVID-19 was RR 0.27 (95%CI 0.09-0.77). Equivalent rate ratios for household members of teachers were 0.97 (95%CI 0.74-1.27) and 0.67 (95%CI 0.36-1.24), and for healthcare workers were 1.82 (95%CI 1.55-2.14) and 1.76 (95%CI 1.22-2.56), respectively.

Ie teachers are as likely to get infected as the general public and about a quarter as likely to get severe infection. Compare to healthcare workers who are more likely than the general population.

Update 2021/02/10: this study from Germany that compared seroprevalence in parents and their children finds that:

The estimated SARS-CoV-2 seroprevalence was low in parents (1.8% [95% CI, 1.2–2.4%]) and 3-fold lower in children (0.6% [95% CI, 0.3-1.0%]). Among 56 families with at least 1 child or parent with seropositivity, the combination of a parent with seropositivity and a corresponding child with seronegativity was 4.3 (95% CI, 1.19-15.52) times higher than the combination of a parent who was seronegative and a corresponding child with seropositivity.

The fact that within households, parents are so much more likely to have been infected than children shows that children cannot be having a meaningful contribution to the pandemic.

Update 2021/02/12: this study in the journal of the American Academy of Pediatrics looking at schools in NC found:

Over 9 weeks, 11 participating school districts had more than 90,000 students and staff attend school in-person; of these, there were 773 community-acquired SARS-CoV-2 infections documented by molecular testing. Through contact tracing, NC health department staff determined an additional 32 infections were acquired within schools. No instances of child-to- adult transmission of SARS-CoV-2 were reported within schools.

Update 2021/02/19: a Swedish study which found:

The number of deaths from any cause among in Sweden who were 1 to 16 years of age was 65 during the pre–Covid-19 period of November 2019 through February 2020 and 69 during 4 months of exposure to Covid-19. From March through June 2020, a total of 15 children with Covid-19 (including those with MIS-C) were admitted to an ICU. Four of the children had an underlying chronic coexisting condition (cancer in 2, chronic kidney disease in 1, and hematologic disease in 1). No child with Covid-19 died.

…Fewer than 10 preschool teachers and 20 schoolteachers in Sweden received intensive care for Covid-19 up until June 30, 2020. As compared with other occupations (excluding health care workers), this corresponded to sex- and age-adjusted relative risks of 1.10 (95% confidence interval [CI], 0.49 to 2.49) among preschool teachers and 0.43 (95% CI, 0.28 to 0.68) among schoolteachers.

Update 2021/02/20: effects of in person vs hybrid vs full remote, shows large losses for all types of education but more for hybrid and remote:

Update 2021/03/17: study in the lancet confirms low mortality in children:

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