Secondary transmission of COVID-19 in preschool and school settings after their reopening in northern Italy: a population-based study

Abstract

BackgroundSchool closures was one of the main measures undertaken to reduce the number of social contacts during the first wave of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. We aimed to describe the data on secondary transmission of SARS-CoV-2 among students and teachers/personnel after the reopening of preschools and schools in Reggio Emilia, Italy.MethodsThis prospective population-based study included all consecutive cases leading to an investigation in 41 classes of 36 educational institutions (8 infant-toddler centres and preschools, 10 primary and 18 secondary schools) in the period September 1 – October 15, 2020, in Reggio Emilia province, Italy. We report the characteristics of the school, of the index case, including the possible source of infection, the number of contacts (students and teachers/personnel) that were identified and tested and the characteristics of secondary cases.ResultsIn the study period, 994 students and 204 teachers were tested during related investigations due to notification of 43 primary cases (38 among students and 5 among teachers). Of these, 10 students and two teachers created 39 secondary cases, resulting in an attack rate of 3.9%. There were no secondary cases among teachers/stuff. Secondary transmission occurred in one primary school and 8 secondary schools. Except for two students and one teacher, the possible source of infection for all index cases was identified as they had all had previous contact with a positive case; the majority of secondary cases did not report any previous close contact with a positive case. The clusters ranged from one to 22 secondary cases.ConclusionsTransmission at school occurred in a non-negligible number of cases, particularly in secondary schools. Prompt testing and isolation of classmates could probably reduce the risk of transmission in school settings.

COVID-19 transmission in educational institutions August to December 2020 in Germany: a study of index cases and close contact cohorts

“…19 Other studies from different settings in Australia, Italy, Ireland, and Singapore also report comparable SARs between 0% and 3%. [20][21][22][23] Compared to students/children, the SAR was higher when the index case was a teacher.…”

“…These numbers are well in line with other published findings on risk of transmission in schools. [19][20][21][22][23][24] One other study from Germany based on 87 school index cases from the DPHA of Frankfurt calculated a slightly higher but comparable SAR of 1•9%. 19 Other studies from different settings in Australia, Italy, Ireland, and Singapore also report comparable SARs between 0% and 3%.…”

“…Although not formally tested in other studies, mainly due to small sample size, descriptive findings in published literature already point towards larger numbers of secondary cases in teacher index cases and support our findings. 21,25,26 In one study from the UK, half of eighteen primary school outbreaks involved teachers only. 25 At the same time, we found that there is only limited transmission from child index cases to teachers, and that such events happen mainly in day-care centres: among a total of 591 student/child index cases, transmission was identified to 25 teachers: (i) thirteen children below six years of age caused 22 secondary infections in day-care teachers, (ii) while three school children caused three infections in school teachers.…”

Kinder und COVID-19: Kontaktpersonen-Surveillance in Frankfurter Kitas und Schulen (August bis Dezember 2020)

“…Oktober E K 204 996 204 994 0 38 0,0 3,2 0,0 3,2 Larosa et al. [ 50 ] Norwegen 2, 3 13 Indexfälle in Schulen Aug.–Nov. 2020 E K k. A.…”

“…In dieser Zeit hatte die COVID-19-Inzidenz in der Gesamtbevölkerung von weniger als 30/100.000 auf über 250/100.000 zugenommen. Keine der 204 untersuchten erwachsenen KP, aber 3,2 % der untersuchten Kinder wurden positiv auf SARS-CoV‑2 getestet [ 50 ]. In Norwegen wurden vom 28.08.2020 bis zum 11.11.2020 KP von 13 Indexfällen in verschiedenen Schulen mittels PCR aus selbst entnommenen Speichelproben – also nicht Rachenabstrichen – untersucht, darunter 234 Kinder und 58 Erwachsene.…”