ARI SHAPIRO, HOST:
New coronavirus cases in Japan have dropped so fast in recent months it seems almost too good to be true. It doesn't look like Japan's previous waves of infections, and it doesn't look like other countries that are in situations similar to Japan's. As NPR's Anthony Kuhn reports, experts are struggling to explain why.
ANTHONY KUHN, BYLINE: In late August, Japan was seeing more than 25,000 new COVID cases a day. The medical system was stretched to its limits, and the situation looked grim to Dr. Hideaki Oka. But by late September, cases had plunged, so Oka is getting a respite.
HIDEAKI OKA: (Through interpreter) We have had zero COVID patients in our hospital for two months straight, so we've been able to concentrate on general medicine, just as in pre-COVID times.
KUHN: Cases dropped by more than 99% from their peak. Japan recorded less than one death a day for weeks, their lowest level since July 2020. Dr. Norio Ohmagari, of Japan's National Center for Global Health and Medicine, summed up the situation in Tokyo at a government meeting on December 9.
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NORIO OHMAGARI: (Through interpreter) We've had below 50 new daily cases on average for eight weeks. We think it is due to countermeasures taken by many citizens and institutions and accelerated vaccination thanks to medical staff's efforts and citizens' understanding.
KUHN: After previous waves of infections, almost as soon as local governments lifted their states of emergencies, cases began to rebound. That hasn't happened this time, although cases appear to be creeping back up.
Dr. Hideaki Oka says that one thing that's changed is that Japan's government speeded up its vaccine rollout ahead of the Olympics, and nearly 80% of its population of 125 million people is now fully vaccinated. The vaccine is one barrier keeping the virus at bay. Oka says that it's a social norm in Japan to keep another kind of barrier over people's mouths and noses.
OKA: (Through interpreter) Even though I keep having no COVID patients, I haven't seen anybody on the street in Japan not wearing masks. Even though they think it may not be necessary, there is pressure for people to do the same as everyone else.
KUHN: But Japan's neighbor, South Korea, has fully vaccinated more than 90% of its adult population and masking up in public is the norm here too, yet South Korea is going through its worst wave of infections of the pandemic so far. Media and scientific journals have published theories that argue that beyond masks and vaccines, there may be something about Japan's people and environment that have helped them to keep cases and deaths low by international standards.
AKIKO IWASAKI: One hypothesis is that there is something intrinsically different about the immune cells that the Japanese people might carry that is able to fight off the infection.
KUHN: Akiko Iwasaki is an immunologist at Yale University. She mentions another theory which says that there are other coronaviruses already in Japan which give people some immunity to COVID. Yet another theory holds that the delta variant in Japan has mutated so that it's less harmful than elsewhere. Iwasaki says these arguments may be interesting, but they're not necessarily correct.
IWASAKI: We just have some tidbits of information that may support these theories, but currently, these are not proven theories.
KUHN: Dr. Hideaki Oka agrees. Japan has barred non-resident foreigners from entering the country to keep out new strains of the virus, but Oka says the restrictions are unsustainable.
OKA: (Through interpreter) Even if the theories are right, it is not possible for Japan to keep the country closed. The reality is another wave will definitely come.
KUHN: And as soon as the next wave of infections hits, he says, it will lay to rest any speculation that Japan is somehow exceptional when it comes to COVID.
Anthony Kuhn, NPR News, Seoul.
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