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Genetic factors, vaccines examined as reasons for Japan's low coronavirus death rate

This supplied electron micrograph shows the new coronavirus that was first identified in the city of Wuhan in central China. (Photo courtesy of the National Institute of Infectious Diseases, Japan)

The death rate among novel coronavirus patients in Japan and other parts of Asia has been low compared to that in Western Europe and North America, sparking interest among news agencies and scientists around the world. Researchers in Japan have raised the possibility of there being genes unique to Japanese people that play a factor in such low fatality rates.

Keio University, Tokyo Medical and Dental University, and other universities established a research team to study the relationship between genes and the development of severe symptoms due to the novel coronavirus, the group announced on May 21. The team will collect blood samples from about 500 to 600 Japanese people who have contracted the novel coronavirus, including those who showed no symptoms. By analyzing the genome sequences and symptoms of each individual, the researchers aim to identify the genes that are connected to severe symptoms. The team plans to organize their findings around this September.

Researchers have investigated the relationship between genes and the development of severe symptoms of infectious diseases in animals. According to Tetsuya Mizutani, professor of virology at Tokyo University of Agriculture and Technology, in cases of leukemia caused by viruses seen in cattle, it is starting to emerge that groupings of multiple genes are related to the development of severe symptoms. He commented, "Inclinations toward developing severe symptoms depending on genetic factors may emerge for COVID-19 as well."

Numerous research institutes overseas including in Australia have been conducting clinical trials regarding the relationship between preventing infections and the use of the bacillus Calmette Guerin (BCG) vaccine, which has garnered worldwide attention. Some feel that one of the reasons why Japan has a small number of infection cases is that this vaccination is given in early childhood. Although its original purpose is to prevent tuberculosis, it is pointed out that the BCG vaccine stimulates the human body's immune system, enhancing the ability to battle other pathogens. However, the World Health Organization issued a statement in April declaring that there is no evidence that the vaccine is effective in preventing coronavirus infections.

In May, a research team in Israel published its findings from a large-scale study conducted on infected people in the Journal of the American Medical Association. In Israel, BCG vaccines used to be carried out on all newborn babies, but the policy was changed from 1982 and only applied to a partial group of immigrants.

The team compared 3,064 individuals born between 1979 and 1981 with 2,869 individuals born between 1983 and 1985, who all had symptoms that suggested they had contracted the coronavirus and had taken polymerase chain reaction (PCR) tests. No significant differences in positive rates for the novel coronavirus could be found, leading the team to conclude that it does not support the idea that BCG vaccines are effective in preventing infections. Meanwhile, as there were few cases of severe symptoms among the sampled individuals, the team said that it could not produce a conclusion between the vaccines and the development of severe symptoms.


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