Japan has almost overnight become a stunning, if somewhat mysterious, coronavirus success story. Every day, a new COVID- From a peak of nearly 6,000 cases in mid-August, caseloads in the densely populated capital are now routinely below 100, an 11-month low.

Despite widespread confusion about what is causing the sharp drop, the bars are packed, the trains are crowded, and the mood is celebratory.

Unlike other parts of Europe and Asia, Japan has never had anything resembling a lockdown, only a series of relatively toothless states of emergency. Some possible factors in Japan’s success include a late but remarkably rapid vaccination campaign, the evacuation of many nightlife areas as fears spread during the recent surge in cases, a widespread practice of wearing masks long before the pandemic, and bad weather in late August that kept people at home.

But, with vaccine efficacy gradually fading and winter approaching, experts are concerned that, without knowing why cases have dropped so dramatically, Japan may face another wave like this summer, when hospitals were overwhelmed with serious cases and deaths skyrocketed — despite the fact that the numbers were lower than pre-vaccination levels. Many people attribute the reduction in infections to the vaccination campaign, particularly among younger people. Almost 70% of the population is fully immunized.

Tateda observed that vaccination rates increased from July to September, just as the more infectious delta variant spread rapidly.

However, he cautioned that breakthrough infections in the United States, the United Kingdom, and other countries where immunizations began months earlier than in Japan demonstrate that vaccines alone are not perfect, and efficacy gradually wears off.

Vaccinations in Japan began in mid-February, with health workers and the elderly first in line. Shortages of imported vaccines slowed progress until late May, when supply stabilized and daily inoculation targets were raised to more than 1 million doses to maximize protection before the Olympics, which take place from July 23 to August 8.

The number of daily shots increased to approximately 1.5 million in July, raising vaccination rates from 15% in early July to 65% by early October, exceeding the 57 percent in the United States.

Daily new cases increased just weeks before the Olympics, forcing Japan to hold the Games in early August with daily caseloads of more than 5,000 in Tokyo and around 20,000 nationwide. Tokyo reported 40 cases on Sunday, the ninth consecutive day with fewer than 100, and the fewest this year. Japan reported 429 cases on Sunday, for a total of approximately 1.71 million cases and 18,000 deaths since the pandemic began early last year.

Though some speculated that the drop in cases was due to less testing, data from the Tokyo Metropolitan Government showed that the positivity rate fell from 25% in late August to 1% in mid-October, while the number of tests fell by one-third. According to Masataka Inokuchi, deputy chief of the Tokyo Medical Association, falling positivity rates indicate that infections have slowed.

Japan’s state of emergency measures were not lockdowns, but rather requests for bars and restaurants to close early and not serve alcohol. Many people continued to commute on crowded trains and to attend sporting and cultural events in stadiums that had some social distancing controls.

The government is gradually increasing social and economic activity while allowing athletic events and package tours on a trial basis using vaccination certificates and increased testing.

To expedite immunizations, former Prime Minister Yoshihide Suga, who recently left office, increased the number of health workers legally permitted to administer shots, opened large-scale vaccination centers, and promoted workplace vaccinations beginning in late June. Hiroshi Nishiura, a Kyoto University professor, told a recent government advisory board meeting that he believes vaccinations helped 650,000 people avoid infection and saved more than 7,200 lives between March and September.

Many experts initially blamed younger people for spreading the virus because they were seen drinking on the streets and in parks when the bars were closed, but data showed that many people in their 40s and 50s also frequented nightlife districts. The majority of serious cases and deaths occurred among unvaccinated people in their 50s and younger.