Daily Covid cases in the country reached more than 23,000 on August 26 but have since fallen sharply to around 100 a day. Photo / AP
Daily Covid cases in the country reached more than 23,000 on August 26 but have since fallen sharply to around 100 a day. Photo / AP
Japan's success in driving down Covid-19 cases has mystified experts but scientists have now identified a genetic "X-factor" among its population that may have helped the country turn its outbreak around.
Daily Covid cases in the country reached more than 23,000 on August 26 but have since fallen sharply to around 100 a day, with numbers remaining steady even as it heads into winter.
Scientists have struggled to explain the dramatic turnaround with some pointing to the influence of some "X-factor". One theory suggested the virus was driven to a "natural extinction" after several mutations led to it being unable to make copies of itself.
However, Japanese researchers from the Riken Institute in Tokyo have now found a possible genetic advantage that may explain the country's success, and published their findings in the British journal Communications Biology last week.
Japan is one of the most vaccinated countries in the world with 77.77 per cent of its total population fully vaccinated. Photo / AP
The researchers found ethnic Japanese people are more likely to have a specific genetic feature related to white blood cells that could be helping the body to fight Covid-19.
"It could be considered an 'X-factor'," Riken immunotherapy laboratory team leader Professor Shin-ichiro Fujii told Nikkei Asia.
The protein located on the surface of white blood cells called HLA-A24, is common among some Asian groups, and is found in about 60 per cent of ethnic Japanese people, but is only present around 10-20 per cent of European and American populations.
Experiments showed that T-cells began to multiply when a peptide extracted from Covid-19's spike protein was added to blood samples containing HLA-A24. The samples also responded to peptides from other seasonal coronaviruses that typically cause colds.
More research is needed to fully understand how the immune system responds.
In this September 13, 2021 file photo, a woman receives the first shot of the Moderna Covid-19 vaccine as others wait for their turn at the pachinko parlour Freedom in Osaka, western Japan. Photo / AP
While the genetic feature may be helping to keep infections down in Japan, the rise in cases in North Korea indicate it's not enough to keep the virus at bay.
Experts believe behavioural change among Japanese people after the Olympics amid a large spike in cases could have helped – including the widespread use of masks and a huge increase in vaccinations.
Japan is one of the most vaccinated countries in the world with 77.77 per cent of its total population fully vaccinated. Australia's rate is slightly lower at 76.67 per cent.
Other measures were also introduced including mandatory temperature checks at some department stores, the provision of hand sanitiser and restrictions on numbers of people in restaurants.
Experts have also been amazed at the low death rates in the country, which has the world's fastest-ageing population, with almost 30 per cent aged 65 years or older.
"The number of deaths is really low," Institution for Future Welfare sociologist Professor Testuo Fukawa told the BBC.
"In 2020, Japanese life expectancy even increased. It's really very special. In other countries – including the United States, UK, Germany, France – all these countries' life expectancy decreased in 2020."
According to Johns Hopkins University, the death rate in Japan from Covid-19 is 14.55 per 100,000. In the United States it is 244.49 per 100,000, although Australia is lower at 8.38 per 100,000.
However, experts are concerned that as protection from vaccinations begins to wear off, and Omicron continues to spread, the county may again see higher cases unless boosters are rolled out.
"The major issue is seasonality. There is a clear seasonal cycle of Covid resurgence – what we observe in Korea will be observed in Japan in terms of parallel resurgent cycle," Tokyo Foundation for Policy Research director Prof Kenji Shibuya told The Telegraph in the UK.
HLA-A24 helps to activate the body's killer T cells and researchers believe that the protein helps T-cells to remember past infections caused by seasonal coronaviruses and to potentially respond when exposed to Covid-19.
