In a recent study published on the Preprint Server medRxiv *, Canadian researchers are exploring the frequency, cluster size and rate of transmission of coronavirus disease (COVID-19) in schools using a simple mathematical model.
To study: COVID-19 clusters in schools: frequency, size and rate of transmission from participatory exposure reports. Image Credit: Prostock-studio / Shutterstock.com
Transmission of SARS-CoV-2 in schools
Current data regarding the role of schools in the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is the virus responsible for COVID-19, is conflicting. Even though COVID-19 in children is generally not as severe as in adults, the risk of multisystem inflammatory syndrome in children (MIS-C) is alarming. In addition, the spread of SARS-CoV-2 in schools can indirectly place vulnerable populations at risk of infection and thus affect the safety of the entire community.
Further studies are needed to determine the involvement of schools in accelerating the transmission of SARS-CoV-2, as previous studies do not provide significant data regarding the role of schools.
About the study
The present study used a generalizable model to determine the heterogenicity of the transmission rate of COVID-19 cases in schools and the variation in cluster size between 2020 and 2021 in four Canadian provinces and eight US states. Canadian data was collected from COVID Schools Canada and US data was obtained from the National Educational Association website. The study also estimated overdispersion parameters from different jurisdictions and their average values.
The data collected included the name of the school, the number of infected students and the date of the report. In Canada, the total number of positive cases, including staff and teachers, was included, while in the United States, only confirmed cases of students were included.
Verification fractions were estimated using overdispersion parameter estimates, which were used to determine the uneven distribution of cases among the various jurisdiction clusters, the fraction present in 20% of the largest clusters. , the time required to achieve a particular cluster size in a jurisdiction, and the distribution of the transmission rate (β) among various index cases. The authors were unable to differentiate the transmission of SARS-CoV-2 occurring in schools from those occurring during children’s social activities outside of school.
Study results
According to the results, Canada had a higher number of clusters, which may be due to their extended period of data collection. The incident rate according to statewide data was highest in the US states. This difference may be due either to the reduced likelihood of reporting smaller clusters or to incomplete data.
Canada had lower observed dispersion than the United States, as the estimated average cluster size from different jurisdictions in the study ranged from 1.3 to 1.7 cases in Canada and from 2 to 8 cases in the United States. . clusters of cases may lead to an upward bias in cluster size and fewer cases detected in a cluster with multiple cases may lead to a downward bias.
Using a simple class transmission model, the transmission rate per contact time per unit time was calculated. The results of the study can be applied to estimate the time required to observe a larger cluster in a jurisdiction. Estimates ranged from five days to over 50 days for the different jurisdictions in the study.
The study did not focus on information on individual-level transmission or the average cluster size of COVID-19; however, using the distribution of a Poisson random variable for cluster size and an underlying gamma-distributed random variable, the rate of transmission was determined.
The effects of social distancing, masking, and bubbling (keeping the contact list constant) have also been studied. To this end, masking and shrinking class size was found to be much more effective in reducing cluster size than bubbling.
Conclusion
The authors propose a simple model that uses cluster size data to obtain information on the average size, transmission rate, and frequency of COVID-19 in schools from data stored in public health facilities without require contact or data tracing at the individual level. The study reports that the bulk of school transmission occurs in a small number of classrooms, with the largest 20% groups accounting for around 80-100% of secondary cases.
The present study developed a method for detecting the rate of individual-to-individual transmission from data on cluster size. Additionally, the results discussed here underscore the importance of data collection to determine cluster size.
The approach used in this study can be generalized to compare other contexts such as outbreaks in the workplace. Additionally, these data help reduce school- or workplace-related transmission of SARS-CoV-2 by providing effective intervention designs.
Most children aged 12 or older in the U.S. and Canadian jurisdictions studied were vaccinated in 2021, as did the general population. This will result in fewer cases of COVID-19 in general, fewer exposures in schools, and fewer clusters. However, the emergence of more infectious variants of SARS-CoV-2 of concern like the Alpha, Delta and Omicron variants may lead to the resurgence of clusters.
*Important Notice
medRxiv publishes preliminary scientific reports that are not peer reviewed and, therefore, should not be considered conclusive, guide clinical practice / health-related behavior, or treated as established information.
“Coffeeaholic. Lifelong alcohol fanatic. Typical travel expert. Prone to fits of apathy. Internet trailblazer.”