Dear Editor,
Restriction of travel against COVID-19 epidemics, if it is limited to a specific area officiating as a prime cause, may be especially of use in the early phase of the transmission, whereas less efficacious in the once widespread stage [1]. Domestic, as well as foreign, travel in Japan has been exceedingly diminished during and even after the “Declaration of a State of Emergency” for the epidemic between 2020/4/7 and 2020//5/25. Despite the second transmission wave in Japan, the government has implemented the 1.35-trillion yen “Go To Travel Campaign” covering a half of travel expenses (up to 20-thousand yen per stay or 10-thousand yen for a day trip) in order to promote domestic travel to any destination since 2020/7/22 ahead of schedule (initially planned early August) merely excluding travel to and from the capital Tokyo. What do we find through the campaign? In the present article, it was examined whether the campaign affected the COPVID-19 epidemic.
Daily new cases in Japan were available on “No. of positive cases, Open data, Current situation in Japan, Situation report, Ministry of Health, Labour and Welfare.” First, data from 2020/6/1 (probable end of the first wave when merely 36 new cases were confirmed) to 2020/7/21 (previous day before the initiation of the campaign on 2020/7/22) were applied to generate logistic-function approximation (2020/6/1–7/21) in accordance with the least-squares regression. Next, the approximated curve was extended after 2020/7/22 as a forecasted curve. All analyses were performed utilizing Microsoft® Excel for Mac version 16.39. Population mobility in retail/recreation were extracted from “Google COVID-19 Community Mobility Reports."
Logistic-function approximation (Fig. 1 ; blue continuous curve during 2020/6/1–7/21) was best-fitted (R 2 = 0.9948) to observed cases (blue open circles). After the initiation of the campaign on 2020/7/22, population mobility in retail/recreation increased with peaks on 2020/7/24 and 2020/8/14–15 (green dotted curve). Despite the campaign and increased population mobility, a peak of observed new cases (red closed circles) was far earlier (7 days before; 2020/8/10 versus 2020/8/17) and lower (−219 cases; 1358 versus 1577 cases) than that of forecasted ones (blue continuous curve).
Fig. 1.
A plot of dates (Day-0 denotes June 1, 2020) on the x-axis and daily COPVID- 19 new cases on the y-axis. Blue open circles, observed cases (7-day moving averages) between June 1 and July 21, 2020; red closed circles, observed cases (7-day moving averages) after July 22 during the "Go To Travel Campaign" (green arrow); blue continuous curve; forecasted curve based on data between June 1 and July 21, 2020; green dotted curve, percent changes (7-day moving averages) of population mobility in retail and recreation. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
The present findings suggest that the “Go To Travel Campaign” in Japan may not have affected the COPVID-19 transmission. Social distancing which may not be often maintained during travel, however, plays an important role in mitigating the epidemic [2]. Limitations in the present study were the following. First, the campaign may not have succeeded in expected increment of tourism. Indeed, however, >2-million people have used the campaign for the first month. Second, the present observational period (approximately 50 days) after the initiation of the campaign may be relatively short to detect its impact on the transmission. It has been reported, however, that daily new cases were correlated to trips 3 weeks before [3] and more cases were confirmed within 11–12 days after population movement [4]. Third, the present logistic-function forecast may be overestimated and accordingly subtract potential augmentation of the epidemic by the campaign.
In conclusion, despite the above-mentioned limitations, the “Go To Travel Campaign” in Japan may not have impacted the COPVID-19 transmission.
Funding
None declared.
Declaration of competing interest
None.
Declaration of competing interest
None declared.
References
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