Does school reopening affect SARS-CoV-2 seroprevalence among school-age children in Milan?

Abstract

The benefits of schools’ closure, used as a containment strategy by many European countries, must be carefully considered against the adverse effects of child wellbeing. In this study, we assessed SARS-CoV-2 seroprevalence, which better estimates the real extent of the infection unraveling asymptomatic cases, among schoolchildren aged 3 to 18 in Milan, using dried blood spot, a safe and extremely viable methods for children, and then compared it between September 2020 and January 2021. Secondly, we evaluated the seroconversion rate and compared it between students attending schools in presence and those switched to distance-learning, using a logistic regression model, both as univariate and multivariate, adjusting for age and biological-sex. Among 1109 pupils, we found a seroprevalence of 2.8% in September before school reopening, while in January 2021, the seropositive rate was 12.5%, reflecting the general growth rate of infections during the second pandemic wave. The overall seroconversion rate was 10%, with no differences based on biological-sex and age groups; we observed no seroreversion. When considered age groups, the seroconversion rate was 10.5% (95%Confidence Interval, 2.9–24.8) among children attending preschools, 10.6% (95%Confidence Interval, 8.2–13.4) for primary schools, 9.9% (95%Confidence Interval, 6.8–13.8) for secondary schools, and 7.8% (95%Confidence Interval, 4–13.2) among high-school students. Interestingly, no differences in seroconversion rate were found between students who attended school compared to those who started remote learning in the first days of November. Furthermore, most patients (61%) reported that the contact occurred within the household. We reported a low seroconversion rate among school children in Milan, with no differences between those who attended from September 2020 to January 2021 compared to those who switched to remote learning in the first days of November. Our data suggest that schools do not amplify SARS-CoV-2 transmission, but rather reflect the level of the transmission in the community.

SARS-CoV-2 PCR and antibody positivity among school staff at the beginning and end of the first school term

“…Low attack rates within schools were also reported from a large study from North Carolina, USA, which included over 100,000 staff and students from 13 school districts [9]. An Italian study did not find any increase in infection incidence among students who attended in-person classes compared with those who attended remote learning [8]. On the other hand, breakdown in infection control practices, e.g.…”

“…While overall evidence suggests little transmission within schools, controversy still exists regarding the role of schools and in-person attendance with spread of infection. Seroprevalence studies over time have suggested low levels on within-school transmission, with majority of the infections acquired outside the school settings [8]. Within the schools, in-person sporting activities have been associated with a higher risk of transmission [9].…”

Epidemiology of SARS-CoV-2 infection among staff and students in a cohort of English primary and secondary schools during 2020–2021

“…29 A study in Italy also found antibody rates rise in teachers over the school year but concluded that school opening did not “amplify transmission”. 48 Attack rates involving staff and students in schools are highly variable across studies, but a recent meta-analysis of five contact-tracing studies found a 10-fold lower attack rate (0.7% of contacts becoming infected) in schools than households (7.6%). 49 …”

Variation in SARS-CoV-2 seroprevalence in children in the region of Asturias, Northern Spain

“…Nevertheless, age was later not identified as a variable independently associated with SARS-CoV-2 seropositivity. There are few studies where higher seropositivity in younger age is described [ 15 , 30 , 31 ]. On the contrary, a lower seroprevalence is often reported in younger children [ 9 , 24 , 26 , 32 ].…”