Estimation of protection for COVID-19 in children from epidemiological information and estimate effect of policy in Japan

Background Incidence in children was much less than in adults during the COVID-19 outbreak. Sports and entertainment events were canceled (VEC) in Japan for two weeks during 26 February – 13 March. Most schools were closed (SC). Object We construct a susceptible–infected–recovered model using three age classes and estimate the basic reproduction number (R 0 ) and protection level among children simultaneously. Then we simulate SC and VEC effects. Method We used data of patients with symptoms in Japan during 14 January to assess SC and VEC introduction. Effects of SC and VEC were incorporated into the model through change in the contact pattern or frequencies among age classes. Results Results: suggest R 0 as 2.86 [95%CI of 2.73, 2.97]. The protection level was estimated as 0.4 [0.2, 0.7]. SC and VEC can reduce the total number of patients significantly, by 6–7%. Discussion and Conclusion The estimated R 0 was similar to that found from other studies in China and Japan. We found a significant protection level among children, and by effects of SC and VEC. Introduction