Comment to Anzai et al., BMC Infectious Diseases (2022)

抄録

Background: Travel subsidy policy during July 22 through December 27, 2020 in Japan, the Go To Travel Campaign (GTC), was believed to have exacerbated the COVID-19 outbreak. A report by Anzai et al. supported this rumor. However, the study specifically examined only two months with only minor changes in GTC.

Object: This study examined the results of the earlier study with a longer time span including periods before and after GTC to confirm the effects of GTC itself, not minor changes.

Method: Following the methods used for the earlier study, we used data of the number of prefectures in which the weekly number of newly confirmed patients per 100 thousand residents was greater than a certain criterion of the daily time trend. Furthermore, we used interaction of the daily time trend and the total number of GTC users per day in the month instead of one time changing in time trend in the earlier study. Two estimation periods were examined: June, 2020 – January, 2021 and May, 2020 – February, 2021.

Results: For both estimation periods, no interaction of the total number of GTC users and the daily time trend was significant in the cases of 3 and 5 day criteria. It was significant, although its coefficient was negative t, for the 7 day criterion.

Discussion and Conclusion: Estimation results indicate that GTC itself or the total number of GTC users might not have worsened COVID-19 outbreak situation. The earlier study had proved that the minor change in GTC in October worsened the outbreak situation temporarily, but those findings might not be appropriate for the entirety of GTC.