It’s hoped that COVID-19 vaccines will be the silver bullet that eventually allows society to return to normal. But even an accelerated inoculation campaign is unlikely to have a major impact on what appears to be a growing fourth wave of infections in Tokyo, according to research by a Tsukuba University professor.

Setsuya Kurahashi, a professor of systems management, conducted a simulation using artificial intelligence that looked at how the vaccine rollout would help prevent the spread of the coronavirus in Tokyo if new infections rise at the same pace as during the second wave last summer.

Even if 70,000 vaccinations per day, or 0.5% of the capital’s 14 million people, were given to Tokyoites — with priority given to people age 60 and over — the capital would still see a fourth wave of infections peaking at 1,610 new cases on May 14, the study showed. The study also showed a fifth wave is expected to peak at 640 cases on Aug. 31.

“The effect of the vaccine inoculations will be observed from July onward, so it’s presumed that it’s dangerous to place too much hope on the effect of the vaccinations for the fourth wave,” Kurahashi wrote.

In addition to the vaccinations, a mechanism that automatically triggers stricter measures if daily new cases exceed a certain threshold, which the study calls a “circuit breaker,” would help curb a fourth wave of infections. Such a system would work as a tool for policymakers to impose a wide-ranging set of measures, similar to those seen in a state of emergency, to restrict people’s contact with one another, such as by shortening business hours, limiting the number of attendees and participants at certain events, increasing the prevalence of telecommuting and asking people to refrain from nonessential outings.

The capital’s outlook could be much more severe if COVID-19 variants begin to spread widely.

Kurahashi last week released a separate simulation study on how variants would likely spread in Tokyo assuming 10 of the roughly 260 new cases confirmed on March 21 were of the U.K. variant. The variant, called B.1.1.7 and first detected last September in the southeast of the U.K., has been raising concerns as it is said to be up to 70% more contagious, and deadlier, than other versions of the virus.

Assuming no circuit breaker measures are taken, but with vaccines given to 70,000 Tokyoites daily, the simulation projected a fifth wave in the capital would peak at an eye-popping 229,300 new cases of the variant on Oct. 20. If the mechanism for tighter measures is put in place once daily numbers exceed 500 cases, however, infections in a fifth wave would peak at 1,700 new cases on the same day.

The study also pointed to a potential benefit of not giving vaccination priority exclusively to older people. According to the research, it is about five times more likely that people age 59 and under infect people age 60 and over rather than the opposite.

For example, if 30% of the 70,000 shots given daily were given to people age 59 and under with the rest administered to older people, that would help reduce daily infections to a peak of 700 cases on Aug. 30, the study said.

Accelerating the vaccination rollout alone won’t be able to prevent a fifth wave of infections, but an effective use of a circuit breaker in addition to adding people under 60 to at least 10% of the priority vaccination lists would prove useful for preventing the spread of the virus, it added.

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