SARS-CoV-2 infection in schools in a northern French city: a retrospective serological cohort study in an area of high transmission, France, January to April 2020

Abstract

Background Children’s role in SARS-CoV-2 epidemiology remains unclear. We investigated an initially unnoticed SARS-CoV-2 outbreak linked to schools in northern France, beginning as early as mid-January 2020. Aims This retrospective observational study documents the extent of SARS-CoV-2 transmission, linked to an affected high school (n = 664 participants) and primary schools (n = 1,340 study participants), in the context of unsuspected SARS-CoV-2 circulation and limited control measures. Methods Between 30 March and 30 April 2020, all school staff, as well as pupils and their parents and relatives were invited for SARS-CoV-2 antibody testing and to complete a questionnaire covering symptom history since 13 January 2020. Results In the high school, infection attack rates were 38.1% (91/239), 43.4% (23/53), and 59.3% (16/27), in pupils, teachers, and non-teaching staff respectively vs 10.1% (23/228) and 12.0% (14/117) in the pupils’ parents and relatives (p < 0.001). Among the six primary schools, three children attending separate schools at the outbreak start, while symptomatic, might have introduced SARS-CoV-2 there, but symptomatic secondary cases related to them could not be definitely identified. In the primary schools overall, antibody prevalence in pupils sharing classes with symptomatic cases was higher than in pupils from other classes: 15/65 (23.1%) vs 30/445 (6.7%) (p < 0.001). Among 46 SARS-CoV-2 seropositive pupils < 12 years old, 20 were asymptomatic. Whether past HKU1 and OC43 seasonal coronavirus infection protected against SARS-CoV-2 infection in 6–11 year olds could not be inferred. Conclusions Viral circulation can occur in high and primary schools so keeping them open requires consideration of appropriate control measures and enhanced surveillance.

Self-testing and vaccination against COVID-19 to minimize school closure

“…The model is parameterized with age-specific estimates of susceptibility, transmissibility, probability of developing symptoms, and probability to detect a case based on symptoms. A systematic review indicates that minors have lower susceptibility to SARS-CoV-2 compared to adults [8], but building evidence suggests that high school aged students may be as susceptible as adults [6], [21]. Here we considered a relative susceptibility of 50% in children and 75% in adolescents compared to adults, and tested homogeneous susceptibility across age for sensitivity.…”

“…Outbreaks in schools [5], [6] are difficult to document, as infections in children are mostly asymptomatic [7] or present mild non-specific symptoms [7]. Despite the lower susceptibility to infections in children compared to adults [8], viral circulation can occur in school settings [6], especially in secondary schools [9]. Accumulating evidence is consistent with increased transmission in the community if schools are in session [9]- [11], and model-based findings suggest that school closure may be used as an additional brake against the COVID-19 pandemic if other social distancing options are exhausted or undesired [12], [13].…”

“…In Europe, depending on the country, students lost from 10 to almost 40 weeks of school from March 2020 to March 2021 due to partial or total school closure (Figure 1). Outbreaks in schools [5], [6] are difficult to document, as infections in children are mostly asymptomatic [7] or present mild non-specific symptoms [7]. Despite the lower susceptibility to infections in children compared to adults [8], viral circulation can occur in school settings [6], especially in secondary schools [9].…”

Prediction of Past SARS-CoV-2 Infections: A Prospective Cohort Study Among Swiss Schoolchildren

“…Retrospectively assessed symptoms might be less reliable to predict past SARS-CoV-2 infections in children. Evidence on non-clinical factors (e.g., SARS-CoV-2 cases in the environment and sociodemographic characteristics) associated with seropositivity in children is scarce (9,11,13) or restricted to specific settings (14,15). In addition, many of these serology studies were conducted at an early stage of the pandemic and therefore represent only the situation at a specific time.…”

Fitting to the UK COVID-19 outbreak, short-term forecasts and estimating the reproductive number

“…Throughout much of our work with this model, the values of α and τ are key in determining behaviour -in particular the role of school children in transmission [16]. We argue that a low τ and a low α are the only combination that are consistent with the growing body of data suggesting that levels of seroprevalence show only moderate variation across age-ranges [17], yet children do not appear to play a major role in transmission [18,19]. To some extent, the separation into symptomatic (D) and asymptomatic (U ) within the model is somewhat artificial as there are a wide spectrum of symptom severity that can be experienced.…”