A Japanese university said Wednesday researchers have found that people are likely to hold antibodies for at least six months after they are infected with the novel coronavirus.
The findings by a Yokohama City University research team suggest that the effect of anti-COVID-19 vaccines being developed by Japan, the United States and other countries -- products that would, if authorized, induce the generation of antibodies in the human body after injection -- may last for some time.
The team will also conduct a study on the antibody status of former COVID-19 patients one year after being infected with the virus, the university said
According to an interim report on the research, 98 percent of 376 people whose blood samples were analyzed had neutralizing antibodies, which work to prevent reinfection by blocking the virus from multiplying.
From August to September, a total of 617 former COVID-19 patients volunteered to take part in the study, which according to the university was the biggest of its kind in Japan, and the team collected blood samples from 376 of them by Oct. 26.
Of the 376 former patients in their 20s to 70s, 280 developed no or mild symptoms, 71 developed moderate symptoms and 25 developed severe symptoms.
The study also found a tendency that antibodies were more prevalent among patients who were moderately or severely affected by the respiratory disease.
While 97 percent of the former patients with no or mild symptoms had neutralizing antibodies after six months, 100 percent of those with moderate or severe symptoms possessed them.
Studies have found that if neutralizing antibodies quickly disappear from the systems of people who recovered from COVID-19, it is difficult to achieve "herd immunity," a development that would make it difficult to put the epidemic under control even after vaccines are made available to the public.
Herd immunity is an indirect protection provided to those who are not immune to an infectious disease when most of a population becomes immune to the disease, according to Johns Hopkins University of the United States.
Since coronavirus vaccines being developed around the world can create neutralizing antibodies, medical experts believe effects could last for a fairly long period of time through vaccinations.
"A number of overseas studies indicate antibodies remain (for several months) in about 90 percent of those who got infected," said Atsushi Goto, a professor at the university's Association of Medical Science and a member of the team.
Goto said the research result is credible as it matches those of studies conducted in foreign countries.
Japan has agreed with US drugmakers Pfizer Inc. and Moderna Inc., as well as Britain's AstraZeneca Plc, to receive sufficient vaccines when they become available.