When masking, vaccinations were used, schools were not a major source of COVID-19 transmission, review finds

An extensive review by McMaster University researchers has found that when infection prevention and control measures were used, schools and daycares weren’t a major source of COVID-19 transmission.

The final living rapid review, published on Feb. 15, 2024 in The Lancet Child and Adolescent Health, marks the culmination of the work by members of the National Collaborating Centre for Methods and Tools (NCCMT) that started in May 2020. The NCCMT is one of six national collaborating centres for public health in Canada.

The review, initially completed in May 2020, was updated 18 times, with the final update conducted at the end of 2022. More than 34,000 references, including databases and websites, were screened as part of these reviews.

“We found that after that initial shutdown where everything was locked down, schools did not appear to have much impact on community level transmission when infection prevention control measures were in place,” said lead author and researcher Sarah Neil-Sztramko, who is also an assistant professor in the Department of Health Research Methods, Evidence and Impact at McMaster University.

However, masking, vaccinations and test-to-stay policies were the most effective at mitigating COVID-19’s spread in schools and daycares. Test-to-stay allowed children who tested negative after a confirmed case in a class to still attend school instead of everyone being part of a two-week quarantine at home.

“It is important to understand which measures mitigate transmission so that schools can remain open as much as possible, given the negative impacts that were found during COVID-19 when they were closed. If there were to be another wave where community transmission was increasing and straining the health-care system, strategies such as masking, vaccination, and test-to-stay interventions are effective in fighting transmission, allowing schools to stay open.”

The living rapid review was continuously updated over two years as new data and studies became available. Researchers previously noted that children under the age of 10 were less likely to drive COVID-19 outbreaks in daycares and schools.

“We were also able to learn what measures were most important when people were vaccinated, and we continued to learn what worked as new evidence emerged throughout the pandemic,” Neil-Sztramko says.

While many of the measures highlighted as effective in curbing COVID-19’s spread are no longer used en masse, Neil-Sztramko believes the findings provide a strong and factual foundation on how to properly deal with significant outbreaks caused by future variants or other infectious diseases.

The NCCMT is hosted by McMaster and funded by the Public Health Agency of Canada (PHAC). The agency had no role in the design, conduct or analysis of the data. PHAC also provided funding to NCCMT to conduct this study.