Japanese researchers have found that people with COVID-19 have antibodies for at least six months after becoming infected.
Yokohama City University and other institutions conducted a study of 376 people in their 20s to 70s who were infected with the coronavirus between February and May.
They analyzed blood samples taken six months after people became infected.
The researchers found that 97 percent of people who were asymptomatic or had mild symptoms, and 100 percent of those with moderate or serious symptoms, had what are called neutralizing antibodies in their systems.
The antibodies are a type of protein produced in the body after an infection. They are believed to weaken viral activities and prevent further infections.
The researchers say that stronger antibodies tended to be found in people who were in serious condition.
The large-scale study suggests that people with the antibodies have a lower risk of infection for at least six months.
Researchers say the finding is good news for vaccine development. They also say they will carry out a follow-up study after another six months.