Japan’s fifth wave of COVID-19 rapidly subsided in recent weeks and a health ministry panel of experts has yet to find a clear answer as to why the number of newly confirmed infections has dropped so dramatically.
One expert is pointing to multiple factors, including the effect of vaccinations and a change in people’s behavior.
During the fifth wave, daily COVID-19 cases confirmed across the country hit a record high of 25,866 on Aug. 20. But the daily count started decreasing later and fell below 1,000 on Oct. 3. Daily cases in Tokyo, which peaked at 5,773 on Aug. 13, dropped to under 100 on Oct. 4 and are currently standing at around 50 to 60, levels last seen in late June 2020.
As of Sept. 13, about half of the country’s population had been fully vaccinated against the coronavirus. As of Friday, the proportion came to 66.1%, with 74.7% of the population having received at least one dose.
Multiple surveys have confirmed the high efficacy of COVID-19 vaccines. In March to September, vaccinations helped some 650,000 people avoid infection while curbing fatalities by about 7,200, according to an estimate presented to a recent meeting of the health ministry panel.
In a survey by the Wakayama Prefectural Government, 81% of the 235 people who contracted the virus from July to September after getting fully vaccinated did not cause secondary infections while a total of 72% of unvaccinated people and those with a single vaccine shot were found to have transmitted the virus to others after getting infected themselves.
“Vaccines are effective in preventing the spread of infections within a community,” a prefectural government official said.
Tokyo Medical University professor Atsuo Hamada cited multiple factors behind the recent sharp decrease in new cases.
Specifically, Hamada said that more and more people are getting vaccinated and that from around mid-August, following the Tokyo Olympics, many people started to refrain from taking actions that increase the risk of infection amid extensive media coverage of the coronavirus surge.
In addition, people began to appropriately ventilate indoor spaces after the summer heat subsided in late August, he said.
“The delta variant is more transmissible than the original novel coronavirus, but its virulence may have become weak,” Hamada said, noting that new COVID-19 cases have been decreasing around the world since September.
He also said that there may be a certain number of asymptomatic people infected with the virus who don’t get tested for COVID-19, skewing the official case numbers.
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