Was school closure effective in mitigating coronavirus disease 2019 (COVID-19)? Time series analysis using Bayesian inference

July, 2020

Highlights

• The effectiveness of school closure remains unknown to mitigate the epidemic of COVID-19.
• Time series analyses were conducted using the Bayesian method to evaluate the effectiveness of school closure in Japan.
• The intervention of school closure did not appear to decrease the incidence of coronavirus infection.

Objectives

The Coronavirus disease 2019 (COVID-19) pandemic is causing significant damage to many nations. For mitigating its risk, Japan called on all elementary, junior high and high schools nationwide to close beginning March 1, 2020. However, its effectiveness in decreasing the disease burden has not been investigated.

Methods

We used daily data of the COVID-19 and coronavirus infection incidence in Japan until March 31, 2020. Time series analyses were conducted using the Bayesian method. Local linear trend models with interventional effect were constructed for the number of newly reported cases of COVID-19, including asymptomatic infections. We considered that the effects of the intervention started to appear 9 days after the school closure.

Results

The intervention of school closure did not appear to decrease the incidence of coronavirus infection. If the effectiveness of school closure began on March 9, the mean coefficient α for effectiveness of the measure was calculated to be 0.08 (95% confidence interval -0.36 to 0.65), and the actual reported cases were more than predicted, yet with a rather wide confidence interval. Sensitivity analyses using different dates also did not demonstrate the effectiveness of the school closure.

Discussion

School closure carried out in Japan did not show any mitigating effect on the transmission of novel coronavirus infection.