Interview with Lisa Ferland, epidemiologist and part of the COVID-19 surveillance and response team as an Interim Surveillance Expert at the European Centre for Disease Prevention and Control (ECDC). She comes from the US but lives in Sweden. In addition to her academic background in public health, statistics and information science, Lisa has written a book and is a crowdfunding consultant for authors.
Most countries experienced peak transmission waves when the schools were closed, so how can we be sure about the role of children and/or schools in SARS-CoV-2 transmission?
Lisa Ferland: There are numerous limitations to the current evidence that include, but are not limited to, the unknown proportion of mild and asymptomatic cases in children, case-based surveillance limitations for identifying outbreaks in schools, limited information on testing strategies in school settings, and difficulty detecting ongoing transmission in the school setting versus in the community or household. The ECDC is continuing to monitor the situation as schools reopen in the EU/EEA/UK [European Union, European Economic Area, United Kingdom].
What are the main conclusions we can draw from schools that did not close during the peak of the pandemic in Europe?
Lisa Ferland: In Sweden, children and young people represent a small proportion of the overall number of COVID-19 cases in the country; children often have mild symptoms, if any. In Sweden, teachers and staff were not at an increased risk of contracting COVID-19 compared to other occupations. The closure of schools has other negative effects that must be taken into consideration. Iceland was another country that did not close preschools or primary schools during the peak of the pandemic and there was very limited transmission in the community.
Were you able to compare the risk of infection between settings where masks were mandatory for children and those where they were not?
Lisa Ferland: Nearly all schools in the EU/EEA/UK countries that have a general face mask recommendation do not recommend face masks for children younger than 12. There is currently limited data to assess the risk of infection comparing schools that implement face mask wearing with those that do not.
Do you have information on schools where physical distancing was mandatory for children and those where it was not, and whether there is any difference in the transmission risk?
Lisa Ferland: It is recognised that physical distancing is challenging for the younger age groups, for those under the age of 12, in the preschools and in primary school settings. There is currently limited data to assess the risk of infection comparing schools that implement mandatory physical distancing with those that do not.
Have you noticed any differences among age groups in schoolchildren and teenagers?
Lisa Ferland: In TESSy case-based surveillance data, the proportion of children among hospitalised cases is highest for children aged from 0 to 4, but the crude fatality rate for all age groups from 0 to 18 remains similar. However, this data must be interpreted with great caution due to varying testing policies across age groups and countries.
Investigations of cases identified in school settings suggest that child-to-child transmission in schools is uncommon and not the primary cause of SARS-CoV-2 infection in children whose onset of infection coincides with the period during which they are attending school, particularly in preschools and primary schools.
Children may have a viral load as high as or higher than that of adults. What can this fact tell us?
Lisa Ferland: Many studies have found that children younger than five years of age with mild to moderate COVID-19 symptoms have a higher viral load than older children and adults. Generally, viral load measures are potentially useful markers for infectiousness. However, it remains unclear if children are shedding the virus in a similar manner to adults. Children may be more efficient at spreading the virus in other children than in adults. However, due to children’s mild or asymptomatic presentation coupled with testing strategies focused on testing symptomatic individuals, the extent to which children are spreading the virus in the school setting remains largely unknown.