A Japanese team said Thursday that 97% of people who had caught the original strain of the coronavirus had neutralizing antibodies a year after their infection.
The team, led by Yokohama City University professor Takeharu Yamanaka, conducted an analysis of 250 people who contracted the coronavirus between February and April last year.
For those who caught the coronavirus, the rate at which antibodies remained stood at 98% six months later and 97% a year later, according to the survey.
Among them, the rate came to 97% after six months and 96% after one year for those who developed no or only mild symptoms and 100% for those who suffered medium to severe symptoms.
Meanwhile, when checking whether people had antibodies for coronavirus variants, the rate was 90% both six months and one year later for those who had medium to severe symptoms.
Among those who were without symptoms or mildly ill, the rate fell from 85% after six months to 79% after one year for the variant first detected in Britain, 75% to 69% for the variant first detected in India and 81% to 76% for the one detected in Brazil. The rate was unchanged at 69% for the one first discovered in South Africa.
The survey results suggest that neutralizing antibodies in vaccinated people decrease over time, Yamanaka said, adding that it would be necessary for them to receive fresh inoculations a year later to increase their antibodies.
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