Estimated effectiveness of school closure and voluntary event cancellation as COVID-19 countermeasures in Japan

BACKGROUND: As countermeasures against the COVID-19 outbreak, sports and entertainment events were canceled (VEC) in Japan for two weeks from 26 February through 13 March. Moreover, most schools were closed (SC). OBJECTIVE: For this study, we estimated the basic reproduction number (R(0)) and SC and VEC effects. METHOD: After constructing a susceptible–infected–recovered model with three age classes, we used data of symptomatic patients in Japan for 14 January through 24 March. The SC and VEC effects were incorporated into the model through changes in contact patterns and contact frequencies among age classes. RESULTS: Results suggest R(0) as 2.56, with 95% CI of [2.51, 2.96] before SC and VEC. The respective effects of SC and VEC were estimated as 0.4 (95% CI [0.3, 0.5]) and 0.5 (95% CI [0.3, 0.7]). CONCLUSION: The estimated R(0) is similar to those found from other studies of China and Japan. Significant reduction of contact frequency has been achieved by SC and VEC. Nevertheless, its magnitude was insufficient to contain the outbreak.