Widespread school closures has been one of the most debilitating effects of the Covid-19 pandemic – depriving children of significant chunks of their education, as well as isolating them from their peers.
But now researchers have developed a blueprint for keeping schools open safely in a pandemic: ventilation, masks and smaller class sizes.
Adopting these measures can keep the R rate – the rate at which the virus reproduces – below one in elementary and lower secondary schools.
This means one infected person will infect less than one other person on average, stopping the uncontrolled spread of the virus.
The same measures are also effective in upper secondary schools, if half of the children are vaccinated.
The findings reinforce the view that wearing masks in schools is key in stopping the spread of the Covid-19 virus, just as opposition to mask mandates seems to be gaining the upper hand.
In the U.K., Prime Minister Boris Johnson has told schools to drop the requirement for children to wear masks from today, despite rising Covid-related absence. Many school leaders are ignoring his instruction and continuing to ask students to wear masks in class.
In the U.S., five states have banned universal mask mandates, with five further stat-wide bans blocked, suspended or not enforced. A proposed mask mandate in New York is the subject of ongoing legal action.
A team at the Complexity Science Hub Vienna (CSH) developed a model to simulate the spread of the virus in different school settings, as well the effectiveness of different mitigations. The model assumed that 80% of teachers were vaccinated.
“We clearly see the effectiveness of the so-called Swiss cheese model,” said Peter Klimek of CSH and MedUni Vienna, one of the scientists who put the blueprint together. “No single measure alone can protect one hundred percent, but with several measures combined, protection increases considerably.”
Although the model identified ventilation as the single more effective measure – apart from vaccination – in stopping clusters of infections breaking out, it was the combination of mitigations that meant schools could open safely.
Opening a window for five minutes every 45 minutes resulted in adequate ventilation to curtail the spread of the virus, according to their findings, published today in the journal Nature Communications.
In larger schools, regular testing of teachers also helped reduce the R-rate, as they had more contacts during the day and could carry the virus between classes, the researchers said.
“The correct implementation of measures is the be-all and end-all,” Klimek added. “Even a small deviation – for example, if classes are ventilated less frequently or not all children are getting tested – is enough to make cluster sizes grow exponentially.”
The model was put together using data from 616 coronavirus clusters in Austria during the Delta wave of the virus.
But researcher and lead author of the study Jana Lasser said preliminary data suggests the same measures would be effectivein containing the more contagious Omicron variant, which has become the predominant strain in Europe and North America.
“Due to the much higher infectiousness of Omicron, we need all available measures in all types of schools to prevent larger outbreaks,” she said. Only elementary schools were able to omit one of the mitigations, such as splitting classes, she added.