Useful information

Relationship between travel and the new C19

2021/03/01

There are still many people who have been reluctant to travel since the outbreak of the new
coronavirus infection. Under these circumstances, there have been some papers reporting on
the “Go To Campaign” conducted by the government last year.

Verifying the impact of the Go To Campaign from data from 24 prefectures

One is a paper published in a medical journal called “Journal of Clinical Medicine” by a research
group led by Professor Hiroshi Nishiura of Kyoto University.
This is a study of whether the Go To Campaign has affected the increase in new travel-related
C19 cases in Japan. Approximately 4000 people infected with the new C19 reported from 24
prefectures from May 1st to August 31st, 2020 were analyzed. In 24 prefectures, infected
persons who had a history of cross-prefecture migration or contact with a person who had
migrated within 7 days (or 14 days depending on the prefecture) before the onset of the disease
are also reported. About 20% of the subjects analyzed were “travel-related infected persons”
who had traveled before the onset of symptoms or had contact with travelers.
In this study,
① 30 days before the start of the Go To Campaign (June 22nd to July 21st) = period 1a
② 5 days immediately before the start of the Go To Campaign (July 15-19) = period 1b
③ 5 days immediately after the start of the Go To Campaign (July 22-26) = period 2
④ 24 days after the start of the Go To Campaign (August 8th to 31st) = period 3
The number of infected people per day is compared before and after the Go To Campaign.

Travel-related infections increased after the Go To Campaign

As a result, the number of travel-related infections per day (the number of infected people who
have a travel history or have had contact with travelers) is higher during the Go To Campaign
than before the Go To Campaign (periods 1a and 1b). In the next 30 days (period 2), it
increased as follows.
● Period 2 is 1.4 to 15 times higher than period 1b
● Period 2 is about 3 times that of period 1a
In addition, this study also sorted the subjects by reasons for travel (business, family visit,
tourism), and the following data was limited to travel for tourism purposes.
● Period 2 is 5.7 to 6.8 times that of period 1a
● Period 2 is 1.7 to 2.6 times that of period 1b
I think many people expected that if the movement of people increased during the Go To
Campaign, the infection would spread, and it seems to still be the case when looking at the
data. However, this study does not indicate a causal link proving that the Go To Campaign
increased the number of infected people.

Why did the number of non-travel related infections increase?

However, some questions were raised when this treatise was published.
One is that “there are more non-travel-related infections than travel-related infections.”
In fact, based on the data used in this paper, comparing the number of infected people per day
before and after the Go To Campaign, the number of “non-travel-related infected people” who
had no history of traveling across prefectures or contact with travelers showed a greater
increase.
In response to this point, Professor Nishiura explained in an article sent to m3.com that “people
were brought in by moving and traveling.”
This study targeted Akita, Aomori, Ehime, Fukui, Gunma, Iwate, Kagawa, Kagoshima, Kochi,
Kumamoto, Mie, Nagano, Niigata, Oita, Okayama, Saga, Shiga, Shimane, Shizuoka., Tochigi,
Tokushima, Yamagata, Yamaguchi, Yamanashi, 24 prefectures. In each case, there were almost
no infected people after the end of the first wave of the epidemic. Even before the Go To
Campaign, there were repeated small outbreaks in these areas with travel-related infections.
As a result, Professor Nishiura said that in 24 prefectures where there were few infected people,
the number of non-travel-related infected people increased because “the epidemic first occurred
due to moving across prefectural borders, so it is thought that the infection has increased within
non-travelrelated populations. ”

How high is the risk of infection when traveling?

In addition to this paper, Daigo Nakata of the Institute of Economy, Trade and Industry analyzed
the effect of travel on the risk of new corona infection under the title of “Travel and risk of new
corona infection: analysis by individual data before the third wave”. The results were announced
in January of this year.
The study found that travel “has a significant impact” on the risk of developing infections and the
risk of getting infected with the new corona, and that travel poses a higher risk of infection in
“young people and men” for those who live in the area and have the attribute of having many
direct contacts with friends and acquaintances. For those with the attributes of “older
generation, women, living in non-infected areas, and suppressing direct contact with
acquaintances,” travel was a relatively low or insignificant risk. ”
◎ Reference
“Go To Travel” Campaign and Travel-Associated Coronavirus Disease 2019 Cases: A
Descriptive Analysis, July–August 2020
https://www.mdpi.com/2077-0383/10/3/398/htm
Travel and New Corona Infection Risk: Analysis by Individual Data Before the Third Wave
https://www.rieti.go.jp/jp/publications/dp/21j001.pdf