Children aged 5 months to 4 years attending daycare during lockdown from March to May 2020 in France had low levels of SARS-CoV-2 antibodies in their blood – known as seroprevalence – suggesting that levels of viral infections were low in this population.
Research assessing seroprevalence in day care centers that remained open during the first national lockdown in France, suggests that the rate of infection with the SARS-CoV-2 virus was low at 3.7%, with positive cases likely infected with an adult in their household, rather than while in daycare. The seroprevalence rate among daycare staff was similar to that of a control group of adults who were not exposed to children or COVID-positive patients in the workplace.
This study, which included 327 children aged 5 months to 4 years, is the first to estimate preschool seroprevalence and is published in The Lancet Child and Adolescent Health newspaper. Since the study was conducted, a number of variants of SARS-CoV-2 have emerged, which are not captured in the data.
SARS-CoV-2 has been shown to infect people of all ages, however, children tend to develop mild or no symptoms and very rarely need hospitalization. The role of very young children as asymptomatic vectors for the spread of the SARS-CoV-2 virus is still unknown and the risk to the community of having open day care centers is unclear.
The seroprevalence data is believed to reflect the true rate of infection because it shows the levels of antibodies in the blood, whether or not the individual has exhibited symptoms of COVID-19. This study could therefore provide vital information to policy makers regarding the closure of day care centers for very young children during the new waves of the SARS-CoV-2 pandemic, although the authors point out that more research in other settings and Emerging variants will also be needed.
“Our results suggest that daycares are not hotbeds of infection with the SARS-CoV-2 virus and that young children do not spread the virus widely in these environments. These results should be reassuring to parents and staff. day care centers, especially since the children included in the study have parents who are key workers and are believed to be at higher risk during the first wave of the epidemic, ”explains Dr Camille Aupiais, principal author of the Jean-Verdier Hospital, Paris, France. 
COVID-19 has caused more than 2 million deaths worldwide, putting extreme pressure on health systems around the world. Many countries have closed schools and daycares in an attempt to stem infection rates. However, these closures came at an economic cost and raised concerns about the development and well-being of children.
During France’s first national lockdown from March 17 to May 11, 2020, most daycares and schools were closed with a small number operating at reduced capacity to care for the children of critical workers, including healthcare staff and workers social.
All the while, French daycares were urged to follow safety protocols that included working with smaller cohorts of 6-8 children with dedicated staff in each cohort, disinfection of surfaces and face masks, and measurements. social distancing for staff. Parents were not allowed into day care centers and were instructed to screen their children for symptoms of COVID-19 before sending them. Children with symptoms were not allowed to attend day care centers.
The study included 197 daycare workers (average age 40). A staff comparison group of 164 adults (mean age 42) consisted of office and laboratory workers from six hospitals who continued to work during the lockdown and were not professionally exposed to very young children or COVID-19 patients in their workplace.
Data collection took place between June 4 and July 3, 2020, four to eight weeks after the end of national confinement, in nurseries in the French cities of Paris, Rouen and Annecy. Blood samples were taken from the participants – using finger pricks for children – and tested using a rapid lateral flow test to detect SARS-CoV-2 antibodies.
A total of 14/327 children, 14/197 daycare staff and 9/164 reference adults were positive for SARS-CoV-2 antibodies. After adjusting for the sensitivity and specificity of the assay, these values were 3.7%, 6.8% and 5.0%, respectively. Statistically, the seroprevalence rate among daycare staff did not differ significantly from that observed in the comparison group.
The 14 HIV positive children came from 13 day care centers. In the center with two HIV-positive cases, children had attended separate areas of the daycare without mixing, suggesting that there was no child-to-child transmission in these cases.
Contact with a confirmed adult family case of COVID-19 during the lockdown – but not sibling or peer daycare cases – was more common among HIV-positive children than HIV-negative children. Children with HIV were significantly more likely to have at least one HIV positive parent (55% vs. 14%).
The 14 HIV-positive daycares came from eight different daycares and there were two centers with three HIV-positive staff. No difference was found in seroprevalence rates between staff who have been exposed (or not) to a child with confirmed COVID-19.
“Our results suggest that young children are more likely to contract COVID-19 at home, rather than in daycare,” says Dr. Aupiais. “We suggest that clinical signs of COVID-19 are not the best indicator of infection or for testing very young children and that the primary endpoint should be a suspected or confirmed case in an adult member of the household. Further research is needed. necessary to fully understand the role of young children in community transmission. ” 
The authors warn that there are limitations to the study and that new variants of SARS-CoV-2 have emerged since the testing period, including the so-called British, Brazilian and South African variants, and it is not not established whether young children are more or less susceptible to these new strains. Additionally, the daycares included in the study were not operating at full capacity during the study period and the results may not generalize to centers that operate normally outside of the lockdown.
Peer review / Observational study / People
NOTES TO EDITORS
This study was funded by Assistance Publique – Hôpitaux de Paris; Paris City Hall, France and Seine Saint Denis Departmental Council. It was conducted by researchers from the Jean Verdier Hospital, France, Avicenne Hospital, France, Inserm, France, Paris 13 University, Sorbonne Paris Cité, France, University of Paris, France, Armand Trousseau Hospital, France, Robert Debré Hospital , France, Hôpital Annecy Genevois, France, Hôpital André Mignot, France, Hôpital Louis Mourier, France, CHU de Rouen, France, Departmental Council of Seine Saint Denis, France, Service de la Protection Maternelle et Infantile de Paris, France, CHI Créteil , France, Hôpital Antoine Béclère, France, and Clinical and therapeutic association for children of Val de-Marne, France, complete list at the end of the article.
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The Lancet Child and Adolescent Health