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Mandating masks in older children at school is a step forward in preventing the transmission of COVID-19. However, it is insufficient alone. A layered approach to prevention is required, in which physical distancing is one of the most important measures. Masks may be useful as an adjunct to physical distancing, hand and environmental hygiene, and effective building ventilation. Masks are not recommended as a sole measure of prevention due to the inherent difficulties in masking correctly, even for adults. Furthermore, most non-medical/cloth masks have low filtration efficiencies, meaning many viral particles get through.
Countries across Europe and Asia that have opened schools successfully had two things in common: First, they had low rates of COVID-19 transmission in the community and second, they resourced physical distancing, hand hygiene and/or enhanced sanitization measures — at least in the initial stages. Alberta does not have low rates of COVID-19 transmission in the community. In fact, Edmonton has the highest number of active COVID-19 cases to date. The safe re-opening of schools requires prioritizing public health measures, such as the closure of non-essential services (bars, movie theatres) to decrease community transmission.
Guidelines from leading medical journals, the Hospital for Sick Children (Toronto) and the Alberta Health Services Scientific Advisory Group all recommend cohorts or smaller class sizes, enhanced sanitization, and optimizing building ventilation as measures to prevent outbreaks in schools. These public-health interventions required adequate funding. Although some countries were able to relax school safety measures with time without increased outbreaks, this is likely due to low COVID-19 rates in the community as well as variables such as outdoor learning, ability to keep windows open, and baseline small class sizes. In Sweden, where schools remained open throughout the spring, there were very few outbreak investigations in schools due to limited contact tracing capacity, making it problematic to use the country as a model for COVID-19 transmission in schools.