Sweden was one of the few Western countries that kept schools open in the spring of 2020. Pre-schools, primary schools and lower-secondary schools (for those up to age 16) continued with in-person teaching, whereas upper-secondary schools switched to online instruction on March 18th.
Despite this, zero Swedish children died of COVID-19 up to the end of June. In fact, only 15 were admitted to the ICU, and four of these children had a serious underlying health condition.
So keeping schools open didn’t cause any deaths among Swedish children. But did it increase the spread of COVID-19? Although evidence suggests that children are less infectious than adults, their level of infectiousness is not zero. In addition, teachers could transmit the virus to one another in the staff room, and parents could do so when picking their children up from school.
In a paper published in Proceedings of the National Academy of Sciences, researchers from Stockholm and Upsala University examined the impact of keeping schools open on the spread of COVID-19 in Sweden. Their analysis focused on the period from March 25th to June 30th.
The authors used rigorous methods to estimate the causal impact of keeping schools open on COVID-19 outcomes among parents, and among teachers. Specifically, they compared parents whose youngest child was in the last year of lower-secondary school (Year 9) to those whose youngest child was in the first year of upper-secondary school (Year 10).
This method ensured that the two groups of parents were as similar as possible with respect to other possible causes of COVID-19 outcomes. But to be safe, the authors controlled statistically for characteristics like the age, occupation and region of the parents.
They found that there was only one additional positive PCR test per 1,000 parents among those whose youngest child was in the last year of lower-secondary school. They also looked at the number of diagnosed cases of COVID-19, but found this did not differ significantly between the two groups of parents.
When the authors compared teachers from lower-secondary schools with those from upper-secondary schools, the differences were somewhat larger. However, the overall impact of keeping schools open on the spread of COVID-19 was small. The authors estimate that keeping schools open resulted in 620 more cases in a country that saw more than 53,000 up to mid June.
They conclude that closing schools “is a costly measure with potential long-run detrimental effects for students”. And their results are “are in line with theoretical work indicating that school closure is not an effective way to contain SARS-CoV-2”.