Two studies made on monkeys provide some of the first scientific evidence that those treated with Covid-19 can develop immunity to re-infection, a positive sign that the vaccines in question may be successful, say US researchers.
In one new study, researchers infected nine monkeys with Covid-19.
After recovering, the team exposed them to the virus again, but the animals did not get sick.
The findings suggest they are developing natural immunity that protects them from re-exposure, said Dr. Dan Baruch, a researcher at the Center for Virus and Vaccine Research at Harvard’s Bet Izrael Dikonis Medical Center, whose studies were published in the journal Science.
“It’s very good news,” Baruch said. In another study, Baruch and colleagues tested 25 monkeys with six vaccine prototypes to determine if the antibodies produced in response to them provided protection.
They then exposed these monkeys and 10 control animals to the corona virus.
In all controlled animals, the virus appeared in high levels in the nose and lungs, while vaccinated animals had a significant degree of protection, Baruch said.
According to him, eight vaccinated animals were fully protected.
These studies do not prove that people develop immunity or how long it can last, but they are encouraging, the agency said.