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There are likely many factors behind Tokyo’s dramatic fall in new COVID-19 cases, but research shows that one group may be playing a surprising role in ending the fifth wave: the unvaccinated.

Since the peak of the capital’s largest wave of infections, many unvaccinated people have stayed away from places where the virus can spread more easily, such as bars and pubs, a metropolitan government’s researcher has said.

The importance of avoiding such hot spots has been gaining traction since a U.S. study showed just a fraction of places account for the overwhelming majority of infections. The study led by a Stanford University team and other researchers analyzed mobile-phone GPS data and mapped the hourly movements of 98 million people to points of interests such as full-service restaurants and religious establishments.

In the Chicago metropolitan area, for example, 10% of public places, such as restaurants that serve alcohol and hotels, accounted for 85% of the predicted infections, according to the study that has been published in the science and technology journal Nature.

Globally, such has proven to be a reliable indicator that corresponds closely with new COVID-19 infection figures and the virus’s basic reproduction number, which measures the pathogen’s transmissibility. To find similar patterns in the capital, the Tokyo Metropolitan Institute of Medical Science analyzed GPS data to track the movements of people in seven major entertainment areas of Tokyo, including the red-light Kabukicho district, the famous Shibuya Center Street shopping arcade and Roppongi.

The analysis showed that the number of people who went out at night in those potential hot spots has stayed low even over a pair of national holidays this week, while the movements of people in the daytime have been falling for three straight weeks, said Atsushi Nishida, the director of the institute’s Research Center for Social Science & Medicine Sciences. New infection numbers have fallen sharply over the past several weeks, as the majority of residents, including younger people, continue to refrain from dining out in groups, he added.

The Kabukicho entertainment district in Tokyo on June 28 | KYODO
The Kabukicho entertainment district in Tokyo on June 28 | KYODO

There were a little more than 1 million people spending time in those entertainment districts from 6 p.m. to midnight in the week to Sept. 18, down 23.1% from the final week before the current state of emergency was issued in the capital on July 12, the data showed. The decline from noon to 6 p.m. was 16%.

“As a result, the number of those at high risk of infection who go out late at night has fallen to levels equivalent to the lowest level during the first state of emergency last year, and that status has been maintained for at least five weeks,” he told the metropolitan government’s weekly monitoring meeting on Friday. “The (thorough) cooperation of Tokyoites is thought to be behind a sharp decline in infection numbers during that time.”

The daily number of COVID-19 cases in Tokyo fell to a three-month low of 235 on Friday from a high of more than 5,700 on Aug. 13. The coronavirus’s reproduction number was only 0.66 over the past week, meaning on average each infected individual would infect 0.66 person. That’s down from around 1.7 in late July.

But the decline in the number of people going out at night does not fully account for the virus’s low reproduction number, Nishida said, adding that COVID-19 vaccination data also needs to be taken into account, and that’s where restraint among unvaccinated individuals has played a key role.

The number of unvaccinated people who spent time late at night in Tokyo’s busiest entertainment areas has plunged since the Bon holidays in mid-August, he said, contributing to the overall decline.

While more fully vaccinated people are venturing out after a sharp decline during the Bon holidays, outings by the unvaccinated or those who have only received one shot have plummeted to around the lowest levels observed during the first state of emergency last year, Nishida said.

The Kabukicho entertainment district in Tokyo on June 28 | KYODO
The Kabukicho entertainment district in Tokyo on June 28 | KYODO

Research showing the benefits of the Pfizer Inc.-BioNTech and Moderna Inc. vaccines when it comes to preventing severe illness and death, and the subsequent risks for unvaccinated individuals, may have encouraged people who haven’t been inoculated to stay home.

Unvaccinated people accounted for 78.9% of deaths, compared with 11.9% for fully vaccinated people, in a study of 412 people who died in Tokyo between Aug. 1 and Sept. 20, according to data submitted to the monitoring meeting on Friday. The efficacy of the vaccines was starker when looking at deaths among people under age 60, with unvaccinated individuals accounting for 90.8% of the deaths, or 99 cases. One fully vaccinated person in the demographic died from the virus over that period.

As of Thursday, 62.6% of all Tokyoites, excluding medical personnel who were prioritized for vaccination by the government when the rollout began in February, have received at least one COVID-19 shot, while 52.4% are fully vaccinated, according to the metropolitan government data.

Prime Minister Yoshihide Suga has vowed that all those who wish to be vaccinated will be able to receive two shots by the end of November.

While acknowledging the progress in curbing new infections and the easing of the burden on Tokyo’s health care system, the monitoring meeting issued a warning over a possible sharp rise in new cases in the future, which could once again strain the capital’s hospitals.

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