February 15, 2023
TOKYO – Roughly 30% of residents of Tokyo and Osaka Prefecture have acquired antibodies against the novel coronavirus, indicating past infection, according to a survey by the Health, Labor and Welfare Ministry. Infection and vaccination are thought to improve immunity to the virus.
The figure rose significantly from a previous survey conducted in February and March last year, but remains lower than numbers for the United States and European countries.
The government has announced the easing of mask-wearing guidelines, but according to one expert, “As infection spreads more easily in Japan than in other countries, we need to continue to take proper measures against possible infection.”
The survey was conducted in November and December last year on about 8,000 residents age 20 or older in Tokyo and four other prefectures to see if they had antibodies.
The percentage of those with antibodies, which can only be acquired through infection with the virus, was shown to be highest in Osaka Prefecture at 28.8%, followed by 28.2% in Tokyo, 27.1% in Fukuoka Prefecture, 26.5% in Aichi Prefecture and 17.6% in Miyagi Prefecture.
Because of rapid spread of the virus since last summer, the percentage in Miyagi Prefecture surged about 12-fold from the figure in the previous survey.
Overseas, meanwhile, about 80% of individuals in England and 60% of those in the United States are said to possess antibodies.
Though Japan has a high vaccination rate, relatively few people have acquired immunity through infection.
In countries where many people have strong immunity acquired from infection or vaccination, infection spreads slowly even if prevention measures such as mask wearing are relaxed, according to Prof. Satoshi Kutsuna of Osaka University, an expert on infection controls.
“Going forward, Japan will continue to need to be flexible, such as in wearing masks when infections rise, so that the scale of infection stays manageable,” he said.
“If infection prevention measures are simply relaxed, infection will spread quickly in Japan and could result in a rise in deaths,” said Takaji Wakita, director general of the National Institute of Infectious Diseases.