When schools were open for in-person teaching during the COVID-19 pandemic - the nordic experience on control measures and transmission in schools during the delta wave

Abstract

Background Extensive measures to control spread of SARS-CoV-2 have led to limited access to education for millions of children and adolescents during the COVID-19 pandemic. Education and access to schools is vital for children and adolescents’ learning, health, and wellbeing. Based on high vaccine uptake and low incidence levels, the Nordic countries (Denmark, Finland, Iceland, Norway and Sweden) decided to start the academic year 2021/22 with schools open for in-person teaching and moderate mitigation measures. We describe trends in SARS-CoV-2 infections and vaccination coverage among students during the first 12 weeks of the fall semester. Methods In this multinational, retrospective, observational study, we have used surveillance and registry data from each of the Nordic countries to describe vaccine uptake (≥12 years), infection incidence (whole population) and transmission of SARS-CoV-2 among students. The study period, week 30 to 41 (Jul 26th – Oct 17th), represents the autumn semester from immediately before school started until fall break. In addition, we collected information on mitigation measures applied by the respective countries. Results There were slight variations between the countries regarding existing infection prevention and control (IPC) measures, testing strategies and vaccination start-up among adolescents. All countries had high vaccine uptake in the adult population, while uptake varied more in the younger age groups. Incidence in the school-aged population differed between countries and seemed to be influenced by both vaccine uptake and test activity. Infection clusters among school-aged children were described for Denmark and Norway, and the number of clusters per week reflected the incidence trend of the country. Most events consisted of only 1–2 cases. Larger clusters appeared more frequently in the higher grades in Norway and in lower grades in Denmark. Conclusion Data from the Nordic countries indicate that vaccination of adults and adolescents, in addition to mitigation measures, enabled full in-person learning. As SARS-CoV-2 infection does not represent a severe medical risk for most children as previously thought, measures targeting this group should be carefully adjusted and kept at a minimum. Our data add to the evidence on incidence and transmission of SARS-CoV-2 among students in schools open for in-person teaching, and may be valuable for decision makers worldwide.

Factors associated with the formation of SARS-CoV-2 case-clusters in Danish schools: a nationwide register-based observational study

“…National overviews on the occurrence of cases and clusters in schools, including testing rates and vaccination coverage, are, to our knowledge, still scarce in the literature. However, our findings are consistent with data from Norway where more clusters occurred in primary schools than in secondary schools [ 25 , 26 ].…”

“…This does not seem surprising considering that young children were susceptible throughout the majority of the study period as vaccination roll-out for children 5 to 11 years did not begin until the end of November [ 23 ]. A similar trend was seen in the incidence rates in the general Danish population, where the age group 6 to 11 years had the highest incidence among the age groups during the study period [ 24 , 25 ]. National overviews on the occurrence of cases and clusters in schools, including testing rates and vaccination coverage, are, to our knowledge, still scarce in the literature.…”

Characteristics of infections with ancestral, Beta and Delta variants of SARS-CoV-2 in the PHIRST-C community cohort study, South Africa, 2020-2021

“…Several studies have described a shift to increased cases among children and adolescents with the Delta variant but the relative contribution of previous immunity and relaxation of restrictions such as school closures vs intrinsic characteristics of the VOC remains unclear [ 13 , 14 ]. Data on the age distribution of individuals infected with the Beta variant are more limited because of its limited geographic distribution.…”

Characteristics of infections with ancestral, Beta and Delta variants of SARS-CoV-2 in the PHIRST- C community cohort study, South Africa, 2020-2021

“…Several studies have described a shift to increased cases among children and adolescents with the Delta variant but the relative contribution of previous immunity and relaxation of restrictions such as school closures vs intrinsic characteristics of the VOC remains unclear. 13,14 Data are more limited on the Beta variant but a South African surveillance study found an increased incidence of diagnosed cases among individuals aged 1-18 years with the Beta variant compared to ancestral. 15 The same study also found increased incidence with Delta compared to Beta in this age group.…”