Japan’s drop in infections is likely related to a number of factors, says Karen Grépin, a public health professor at Hong Kong University. For one, 77% of Japan is fully vaccinated after its campaign got off to a slow start. Japan has also maintained relatively strict border controls and adopted near universal mask wearing and intensive contact tracing measures even as it avoids mass lockdowns.
Japan isn't alone. Evidence of COVID-19 is also fading in other Asian countries as disparate as Indonesia, India, the Philippines, Singapore, Thailand, and Cambodia. To be sure, countries like South Korea and Vietnam are in the midst of record COVID-19 surges, but the region-wide trend is clear: COVID-19 cases have been dropping across Asia since early September.
Indonesia is recording its lowest level of daily COVID-19 infections since April 2020, with cases falling to 236 from 50,000 in July. The Philippines and India are also recording their lowest daily COVID rates in 18 months.
Michael Toole, an epidemiologist at Australia's Burnet Institute, says improving vaccination rates may be helping. But these countries have likely achieved a “high level of natural immunity,” with Delta-driven waves exposing large portions of their populations to the virus during massive surges earlier this year, he says.
Another potential explanation, at least in some areas, is the weather. While much of Europe may be moving indoors as temperatures drop, people in Asia are transitioning to outdoor activities after brutally hot summers.
"There is also something to be said for seasonality as more pleasant temperatures lead to less crowding," says Jason Tetro, a microbiologist based in Canada and author of The Germ Code. "In places like Japan, Singapore, and Indonesia, it could also be in those very hot summer months when people simply need to get into the cooler indoor air."
But ultimately, scientists say that much of the why and when of COVID-19 waves remains a mystery.
“Although we are two years into COVID-19, we still have few answers regarding surges and drop-offs,” says Tetro.