Age-dependency of the Propagation Rate of Coronavirus Disease 2019 Inside School Bubble Groups in Catalonia, Spain

Child mask mandates for COVID-19: a systematic review

BACKGROUND

Mask mandates for children during the COVID-19 pandemic varied in different locations. A risk-benefit analysis of this intervention has not yet been performed. In this study, we performed a systematic review to assess research on the effectiveness of mask wearing in children.

METHODS

We performed database searches up to February 2023. The studies were screened by title and abstract, and included studies were further screened as full-text references. A risk-of-bias analysis was performed by two independent reviewers and adjudicated by a third reviewer.

RESULTS

We screened 597 studies and included 22 in the final analysis. There were no randomised controlled trials in children assessing the benefits of mask wearing to reduce SARS-CoV-2 infection or transmission. The six observational studies reporting an association between child masking and lower infection rate or antibody seropositivity had critical (n=5) or serious (n=1) risk of bias; all six were potentially confounded by important differences between masked and unmasked groups and two were shown to have non-significant results when reanalysed. Sixteen other observational studies found no association between mask wearing and infection or transmission.

CONCLUSIONS

Real-world effectiveness of child mask mandates against SARS-CoV-2 transmission or infection has not been demonstrated with high-quality evidence. The current body of scientific data does not support masking children for protection against COVID-19.

Policies on children and schools during the SARS-CoV-2 pandemic in Western Europe

During the pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), mitigation policies for children have been a topic of considerable uncertainty and debate. Although some children have co-morbidities which increase their risk for severe coronavirus disease (COVID-19), and complications such as multisystem inflammatory syndrome and long COVID, most children only get mild COVID-19. On the other hand, consistent evidence shows that mass mitigation measures had enormous adverse impacts on children. A central question can thus be posed: What amount of mitigation should children bear, in response to a disease that is disproportionally affecting older people? In this review, we analyze the distinct child versus adult epidemiology, policies, mitigation trade-offs and outcomes in children in Western Europe. The highly heterogenous European policies applied to children compared to adults did not lead to significant measurable differences in outcomes. Remarkably, the relative epidemiological importance of transmission from school-age children to other age groups remains uncertain, with current evidence suggesting that schools often follow, rather than lead, community transmission. Important learning points for future pandemics are summarized.

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

A register-based retrospective observational study was conducted to describe SARS-CoV-2 cases and case-clusters in schoolchildren of Danish primary and lower secondary schools and identify which factors were associated with the occurrence of case-clusters in schools. The study period was the autumn school semester 2021. Clusters were defined as three or more cases in a school-class level within 14 days. Descriptive analysis was carried out and multivariable logistic regression analysis was performed to determine which factors were associated with case introductions (i.e., primary case) being linked to a cluster. More cases and clusters were identified in lower than in higher class levels. Out of 21,497 cases introduced into a school, 41.6% started a cluster. A higher assumed immunity level in a class level was significantly reducing the odds of a case introduction being linked to a cluster (e.g., assumed immunity of ≥80% vs <20%: OR: 0.28; 95%CI: 0.17-0.44). A previous infection (in the primary case) had a protective effect (OR: 0.58; 95%CI: 0.33-0.99). This study suggests that most cases appearing in schools did not induce clusters, but that once cluster occur sizes can be large. It further indicates that vaccination of children markedly reduces the risk of secondary infections.

SARS-CoV-2 transmission in teenagers and young adults in Fútbol Club Barcelona's Multidisciplinary Sports Training Academy

Most studies, aimed at determining the incidence and transmission of SARS-CoV-2 in children and teenagers, have been developed in school settings. Our study conducted surveillance and inferred attack rates focusing on the practice of sports. Prospective and observational study of those attending the sports facilities of Fútbol Club Barcelona (FCB), in Barcelona, Spain, throughout the 2020-2021 season. Participants were young players (from five different sports) and adult workers, who belonged to stable teams (shared routines and were involved in same quarantine rules). Biweekly health questionnaires and SARS-CoV-2 screening were conducted. From the 234 participants included, 70 (30%) both lived and trained in the FCB facilities (Recruitment Pathway 1;RP1) and 164 (70%) lived at their own household and just came to the facilities to train (RP2). During the study, 38 positive cases were identified; none had severe symptoms or needed hospitalization. The overall weekly incidence in the cohorts did not differ compared to the one expected in the community, except for 2 weeks when an outbreak occurred. The attack rate (AR) was three times higher for the participants from RP1, in comparison to those from RP2 (p < 0.01). A Basketball team showed a significant higher AR.  Conclusion: Physical activities in stable teams are not related to an increased risk of transmission of SARS-CoV-2, since there were the same observed cases than expected in the community. The risk is higher in indoor sports (Basketball vs. Football), and in closed cohort living settings (RP1 vs. RP2). The fulfilment of preventive measures is essential. What is Known: • Despite the low numerical impact caused in paediatric hospitalizations during COVID-19 pandemic, the social impact has been maximum. • The transmission potential in children and teenagers is limited, and it had been widely demonstrated in school settings. What is New: • Group physical activities in children and teenagers are not also related to an increased risk of transmission of SARS-CoV-2, when preventive measures, such as washing hands, and screening protocols are applied. • Routine and semi-professional sports activities seem safe environments to promote during this pandemic.

IMPACTO DE LA VACUNACIÓN CONTRA SARS-CoV-2 EN LA INCIDENCIA DE INFECCIÓN EN ÁMBITO ESCOLAR

Antecedentes.

La pandemia por SARS-CoV-2 afectó a la población en edad escolar debido a la propia enfermedad y, al mismo tiempo, por las medidas aplicadas de prevención y control de la infección. El objetivo del estudio fue evaluar el efecto de la vacunación poblacional contra COVID-19 en la incidencia de infección en ámbito escolar.

Materiales y métodos.

Se realizó un estudio descriptivo retrospectivo de casos y brotes escolares por COVID-19 a nivel provincial. Se incluyó alumnado, docentes y personal de diferentes etapas educativas de los centros. La medida principal de resultados fue la incidencia acumulada en función de etapa educativa, perfil del caso y clínica durante el primer trimestre del curso 2020/2021 frente al mismo periodo 2021/2022.

Resultados.

La incidencia total de infección por SARS-CoV-2 en las aulas fue de 2.470 casos por cada 100.000 habitantes en el primer trimestre del curso 2020/2021 y de 2.720 casos por cada 100.000 habitantes en el mismo periodo 2021/2022. El número de brotes escolares notificados fue 7 veces mayor en este segundo periodo; y, al mismo tiempo, el riesgo de infección en las aulas de mayores de 12 años (alumnos y docentes) se redujo un 43,1% (vacunados en elevado porcentaje).

Conclusiones.

Este estudio muestra menor transmisión de infección por SARS-CoV-2 en los alumnos de las etapas educativas superiores (Secundaria y Bachillerato) durante el primer trimestre escolar 2021/2022 (grupo con elevada cobertura vacunal al inicio del período) respecto al curso previo (sin vacunación).

SARS-CoV-2 infection characteristics among students and staff in a large high school COVID-19 outbreak and secondary transmission in households

Background

SARS-CoV-2 clinical presentation is associated with the patients' age group. Overall, young individuals present higher proportions of asymptomatic or mild COVID-19 infection, compared to adults. Data on secondary COVID-19 transmission in households, according to the cases' age group, are accumulating.

Methods

We performed a follow-up cohort study including all COVID-19 real-time polymerase chain reaction (RT-PCR)-confirmed cases (adolescent students and school staff) diagnosed in an epidemiological investigation of a large high school outbreak. We compared the adolescent and adult groups regarding clinical symptoms, time to negative COVID-19 RT-PCR tests, and infection transmission in households.

Results

The study population included 817 persons. The confirmed COVID-19 RT-PCR outbreak cases (n = 178) were followed (students aged 12-19 years, median age 14 years, n = 153, school staff aged 24-67 years, median age 39 years, n = 25) and the cases' household close contacts (n = 639) were tested. The adolescents had lower symptomatic infection rates, shorter time to negative COVID-19 RT-PCR tests, and lower transmission rates to household members, compared to the adults. The general transmission rate among household contacts was 13.5%, (86/639) ranging from 8.6% in asymptomatic students' contacts to 27.3% in symptomatic staff contacts. COVID-19 transmission rates were significantly higher in contacts of symptomatic cases compared to asymptomatic cases (odds ratio: 2.06, 95% CI 1.26-3.4) and higher in adults compared to adolescents (odds ratio: 2.69, 95% CI 1.43-4.89).

Conclusions

Adolescents and adults diagnosed in an outbreak investigation differ as to COVID-19 clinical presentation and transmission. As adolescents may show mild or no symptoms, COVID-19 prevention in school settings is challenging. Implementing nonpharmaceutical measures and promoting vaccination programs in eligible staff and students should be considered.

Unravelling the role of the mandatory use of face covering masks for the control of SARS-CoV-2 in schools: a quasi-experimental study nested in a population-based cohort in Catalonia (Spain)

OBJECTIVE

To assess the effectiveness of mandatory use of face covering masks (FCMs) in schools during the first term of the 2021-2022 academic year.

DESIGN

A retrospective population-based study.

SETTING

Schools in Catalonia (Spain).

POPULATION

599 314 children aged 3-11 years attending preschool (3-5 years, without FCM mandate) and primary education (6-11 years, with FCM mandate).

STUDY PERIOD

From 13 September to 22 December 2021 (before Omicron variant).

INTERVENTIONS

A quasi-experimental comparison between children in the last grade of preschool (5 years old), as a control group, and children in year 1 of primary education (6 years old), as an interventional group.

MAIN OUTCOME MEASURES

Incidence of SARS-CoV-2, secondary attack rates (SARs) and effective reproductive number (R*).

RESULTS

SARS-CoV-2 incidence was significantly lower in preschool than in primary education, and an increasing trend with age was observed. Six-year-old children showed higher incidence than 5 year olds (3.54% vs 3.1%; OR 1.15 (95% CI 1.08 to 1.22)) and slightly lower but not statistically significant SAR (4.36% vs 4.59%; incidence risk ratio 0.96 (95% CI 0.82 to 1.11)) and R* (0.9 vs 0.93; OR 0.96 (95% CI 0.87 to 1.09)). Results remained consistent using a regression discontinuity design and linear regression extrapolation approaches.

CONCLUSIONS

We found no significant differences in SARS-CoV-2 transmission due to FCM mandates in Catalonian schools. Instead, age was the most important factor in explaining the transmission risk for children attending school.

The next 'pandemic playbook' needs to prioritize the needs of children-and a clear roadmap for opening schools

The national influenza pandemic response plan includes short-term school closures as an infection mitigation measure, based on modeling data regarding the role of pediatric populations and schools as drivers of disease spread. Modeled estimates regarding the role of children and their in-school contacts as drivers of community transmission of endemic respiratory viruses were used in part to justify prolonged school closures throughout the United States. However, disease transmission models extrapolated from endemic pathogens to novel ones may underestimate the degree to which spread is driven by population immunity and overestimate the impact of school closures as a means of reducing child contacts, particularly in the longer-term. These errors, in turn, may have caused incorrect estimations about the potential benefits of closing schools on a society level while simultaneously failing to account for the significant harms of long-term educational disruption. Pandemic response plans need to be updated to include nuances regarding drivers of transmission such as pathogen type, population immunity, and contact patterns, and disease severity in different groups. Expected duration of impact also needs to be considered, recognizing that effectiveness of different interventions, particularly those focused on limiting social interactions, are short-lived. Additionally, future iterations should include risk-benefit assessments. Interventions that are particularly harmful to certain groups, such as school closures are on children, should be de-emphasized and time limited. Finally, pandemic responses should include ongoing and continuous policy re-evaluation and should include a clear plan for de-implementation and de-escalation.

Transmisión del SARS-CoV-2 en escolares durante el primer trimestre del curso 2021/2022 en la provincia de Albacete: incidencia e impacto de las nuevas variantes

OBJECTIVE

The objective of this study was to know the evolution of the COVID-19 pandemic in the school setting, and the effect of the new variants on it.

DESIGN

It is an observational longitudinal descriptive study during the first term of the academic year 21/22. SITE: Community health services.

PARTICIPANTS

Preschool, elementary, secondary, and high school students.

INTERVENTIONS

none.

MAIN MEASUREMENTS

We calculated cumulative incidence stratified by grade, source of infection and follow-up period, percentage of vaccinated cases and correlation between cumulative incidence in schooled children per week and cumulative incidence in the general population.

RESULTS

1526 cases were reported, and the cumulative incidence was 3,17% and 0,48% in within-school acquired cases. 20,9% were vaccinated. During follow-up, there was an important change in incidence from weeks 49/21 on, at the time Omicron began to appear in Spain, with an increase in secondary cases, mostly high school students. We found a high correlation between general population and schooled children's cumulative incidence (R2 = 0,59).

CONCLUSIONS

SARS-CoV-2 transmission in school settings has been affected by new circulating variants. Two propagation scenarios were identified, and they were like the community propagation pattern. This supports the hypothesis that school settings reflect the transmission in the community. Reinforcement of preventive measures and surveillance would have a positive effect on school settings.

Preventive behavior against SARS-CoV-2 infection in adults according to whether or not they live with children. A combined analysis of the nationwide COSMO-SPAIN and ENE-COVID surveys

Introduction

The protection of children is a major driver of behavior among those in charge of their care. We evaluated whether compliance with preventive measures against SARS-CoV-2 infection among adults living with children was different from that of those not living with them, in 2020.

Methods

We used the COSMO-SPAIN (N = 867) and the nationally representative ENE-COVID (N = 29,926) surveys to estimate prevalence of compliance (95% confidence interval). Logistic model based standardization methods were applied to estimate standardized prevalence differences (SPrD) to the overall distribution of age, sex, education, history of COVID-19, and residence of other >60 yrs in the household.

Results

We observed that adults living with children more frequently avoided bars (SPrD_ENE-COVID: 4.2%; 95% CI: 2.3-6.1), crowded places (SPrD_COSMO: 8.0%; 95% CI: 0.6-15.1) and did not use public transportation (SPrD_ENE-COVID: 4.9%; 95% CI: 3.0-6.7). They were also more worried about work and family conciliation (SPrD_COSMO: 12.2%; 95% CI: 4.8-19.5) and about closure of education centers (SPrD_COSMO: 26.5%; 95% CI: 19.4-33.6).

Discussion

In general, adults living with children adopted slightly more frequently social distancing measures.

Surveillance of Acute SARS-CoV-2 Infections in Elementary Schools and Daycare Facilities in Bavaria, Germany (09/2020-03/2021)

Introduction

Here we report our results of a multi-center, open cohort study ("COVID-Kids-Bavaria") investigating the distribution of acute SARS-CoV-2 infections among children and staff in 99 daycare facilities and 48 elementary schools in Bavaria, Germany.

Materials and Methods

Overall, 2,568 children (1,337 school children, 1,231 preschool children) and 1,288 adults (466 teachers, 822 daycare staff) consented to participate in the study and were randomly tested in three consecutive phases (September/October 2020, November/December 2020, March 2021). In total, 7,062 throat swabs were analyzed for SARS-CoV-2 by commercial RT-PCR kits.

Results

In phase I, only one daycare worker tested positive. In phase II, SARS-CoV-2 was detected in three daycare workers, two preschool children, and seven school children. In phase III, no sample tested positive. This corresponds to a positive test rate of 0.05% in phase I, 0.4% in phase II and 0% in phase III. Correlation of a positive PCR test result with the local-7-day incidence values showed a strong association of a 7-day-incidence of more than 100/100,000 as compared to <100/100,000 (OR = 10.3 [1.5-438], p < 0.005). After phase III, antibody testing was offered to 713 study participants in elementary schools. A seroprevalence rate of 7.7% (students) and 4.5% (teachers) was determined.

Discussion

During the initial waves of the SARS-CoV-2 pandemic, the risk of a positive SARS-CoV-2 result correlated positively with the local 7-day incidence. Hence, the occurrence of SARS-CoV-2 infections were reflected in schools and daycare facilities. An increased risk of SARS-CoV-2 transmission in the setting of daycare and elementary schooling was unlikely.

Transmission of SARS-CoV-2 in Norwegian schools during academic year 2020-21: population wide, register based cohort study

Objective

To assess the risk of transmission of SARS-CoV-2 in schools in Norway mainly kept open during the covid-19 pandemic in the academic year 2020-21.

Design

Population wide, register based cohort study.

Setting

Primary and lower secondary schools in Norway open during the academic year 2020-21, with strict infection prevention and control measures in place, such as organisation of students into smaller cohorts. Contact tracing, quarantine, and isolation were also implemented, and testing of students and staff identified as close contacts.

Participants

All students and educational staff in primary and lower secondary schools in Norway, from August 2020 to June 2021.

Main outcome measures

Overall attack rate of SARS-CoV-2 transmission (AR14) was defined as the number of individuals (among students, staff, or both) in the school with covid-19, detected within 14 days of the index case, divided by the number of students and staff members in the school. AR14 to students (attack rates from all index cases to students only) and AR14 to school staff (attack rates from all index cases to staff members only) were also calculated. These measures for student and school staff index cases were also calculated separately to explore variation in AR14 based on the characteristics of the index case.

Results

From August 2020 to June 2021, 4078 index cases were identified; 3220 (79%) students and 858 (21%) school staff. In most (2230 (55%)) schools with an index case, no subsequent individuals with covid-19 were found within 14 days; in 631 (16%) schools, only one more individual with covid-19 within 14 days was found. Overall, AR14 was 0.33% (95% confidence interval 0.32% to 0.33%). When restricting index cases and subsequent individuals with covid-19 to students born in the same year, AR14 to students (0.56-0.78%) was slightly higher.

Conclusions

Regarding the number of people infected with SARS-CoV-2 among students and staff, these results suggest that schools were not an important setting for transmission of the virus in Norway during the covid-19 pandemic in the academic year 2020-21.

Considerations for the Safe Operation of Schools During the Coronavirus Pandemic

During the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, providing safe in-person schooling has been a dynamic process balancing evolving community disease burden, scientific information, and local regulatory requirements with the mandate for education. Considerations include the health risks of SARS-CoV-2 infection and its post-acute sequelae, the impact of remote learning or periods of quarantine on education and well-being of children, and the contribution of schools to viral circulation in the community. The risk for infections that may occur within schools is related to the incidence of SARS-CoV-2 infections within the local community. Thus, persistent suppression of viral circulation in the community through effective public health measures including vaccination is critical to in-person schooling. Evidence suggests that the likelihood of transmission of SARS-CoV-2 within schools can be minimized if mitigation strategies are rationally combined. This article reviews evidence-based approaches and practices for the continual operation of in-person schooling.

COVID-19 pandemic. What have we learned?

Since the COVID-19 pandemic was declared in March 2020, we have learned a lot about the SARS-CoV-2 coronavirus, and its role in pediatric pathology. Children are infected in a rate quite similar to adults, although in most cases they suffer mild or asymptomatic symptoms. Around 1% of those infected require hospitalization, less than 0.02% require intensive care, and mortality is very low and generally in children with comorbidities. The most common clinical diagnoses are upper or lower respiratory infections, gastrointestinal infection and, more seriously, multisystemic inflammatory syndrome (MIS-C). Most episodes do not require treatment, except for MIS-C. Remdesivir has been widely used as a compassionate treatment and its role has yet to be defined. The newborn can become infected, although vertical transmission is very low (<1%) and it has been shown that the baby can safely cohabit with its mother and be breastfed. In general, neonatal infections have been mild. Primary care has supported a very important part of the management of the pandemic in pediatrics. There has been numerous collateral damage derived from the difficulty of access to care and the isolation suffered by children. The mental health of the pediatric population has been seriously affected. Although it has been shown that schooling has not led to an increase in infections, but rather the opposite. It is essential to continue maintaining the security measures that make schools a safe place, so necessary not only for children's education, but for their health in general.

[COVID-19 pandemic. What have we learned?]

Since the COVID-19 pandemic was declared in March 2020, we have learned a lot about the SARS-CoV-2 coronavirus, and its role in pediatric pathology.Children are infected in a rate quite similar to adults, although in most cases they suffer mild or asymptomatic symptoms. Around 1% of those infected require hospitalization, less than 0.02% require intensive care, and mortality is very low and generally in children with comorbidities. The most common clinical diagnoses are upper or lower respiratory infections, gastrointestinal infection and, more seriously, multisystemic inflammatory syndrome (MIS-C). Most episodes do not require treatment, except for MIS-C. Remdesivir has been widely used as a compassionate treatment and its role has yet to be defined.The newborn can become infected, although vertical transmission is very low (<1%) and it has been shown that the baby can safely cohabit with its mother and be breastfed. In general, neonatal infections have been mild.Primary care has supported a very important part of the management of the pandemic in pediatrics. There has been numerous collateral damage derived from the difficulty of access to care and the isolation suffered by children. The mental health of the pediatric population has been seriously affected. Although it has been shown that schooling has not led to an increase in infections, but rather the opposite. It is essential to continue maintaining the security measures that make schools a safe place, so necessary not only for children's education, but for their health in general.

The impact of school opening model on SARS-CoV-2 community incidence and mortality

The role that traditional and hybrid in-person schooling modes contribute to the community incidence of SARS-CoV-2 infections relative to fully remote schooling is unknown. We conducted an event study using a retrospective nationwide cohort evaluating the effect of school mode on SARS-CoV-2 cases during the 12 weeks after school opening (July-September 2020, before the Delta variant was predominant), stratified by US Census region. After controlling for case rate trends before school start, state-level mitigation measures and community activity level, SARS-CoV-2 incidence rates were not statistically different in counties with in-person learning versus remote school modes in most regions of the United States. In the South, there was a significant and sustained increase in cases per week among counties that opened in a hybrid or traditional mode versus remote, with weekly effects ranging from 9.8 (95% confidence interval (CI) = 2.7-16.1) to 21.3 (95% CI = 9.9-32.7) additional cases per 100,000 persons, driven by increasing cases among 0-9 year olds and adults. Schools can reopen for in-person learning without substantially increasing community case rates of SARS-CoV-2; however, the impacts are variable. Additional studies are needed to elucidate the underlying reasons for the observed regional differences more fully.

Schools as a Framework for COVID-19 Epidemiological Surveillance of Children in Catalonia, Spain: A Population-Based Study

Objective: We describe and analyze the childhood (<18 years) COVID-19 incidence in Catalonia, Spain, during the first 36 weeks of the 2020-2021 school-year and to compare it with the incidence in adults. Methods: Data on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) tests were obtained from the Catalan Agency for Quality and Health Assessment. Overall, 7,203,663 SARS-CoV-2 tests were performed, of which 491,819 were positive (6.8%). We collected epidemiological data including age-group incidence, diagnostic effort, and positivity rate per 100,000 population to analyze the relative results for these epidemiological characteristics. Results: Despite a great diagnostic effort among children, with a difference of 1,154 tests per 100,000 population in relation to adults, the relative incidence of SARS-CoV-2 for <18 years was slightly lower than for the general population, and it increased with the age of the children. Additionally, positivity of SARS-CoV-2 in children (5.7%) was lower than in adults (7.2%), especially outside vacation periods, when children were attending school (4.9%). Conclusions: A great diagnostic effort, including mass screening and systematic whole-group contact tracing when a positive was detected in the class group, was associated with childhood SARS-CoV-2 incidence and lower positivity rate in the 2020-2021 school year. Schools have been a key tool in epidemiological surveillance rather than being drivers of SARS-CoV-2 incidence in Catalonia, Spain.

Schools as a Framework for COVID-19 Epidemiological Surveillance of Children in Catalonia, Spain: A Population-Based Study

Objective: We describe and analyze the childhood (<18 years) COVID-19 incidence in Catalonia, Spain, during the first 36 weeks of the 2020-2021 school-year and to compare it with the incidence in adults. Methods: Data on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) tests were obtained from the Catalan Agency for Quality and Health Assessment. Overall, 7,203,663 SARS-CoV-2 tests were performed, of which 491,819 were positive (6.8%). We collected epidemiological data including age-group incidence, diagnostic effort, and positivity rate per 100,000 population to analyze the relative results for these epidemiological characteristics. Results: Despite a great diagnostic effort among children, with a difference of 1,154 tests per 100,000 population in relation to adults, the relative incidence of SARS-CoV-2 for <18 years was slightly lower than for the general population, and it increased with the age of the children. Additionally, positivity of SARS-CoV-2 in children (5.7%) was lower than in adults (7.2%), especially outside vacation periods, when children were attending school (4.9%). Conclusions: A great diagnostic effort, including mass screening and systematic whole-group contact tracing when a positive was detected in the class group, was associated with childhood SARS-CoV-2 incidence and lower positivity rate in the 2020-2021 school year. Schools have been a key tool in epidemiological surveillance rather than being drivers of SARS-CoV-2 incidence in Catalonia, Spain.