Two studies in monkeys have discovered the first scientific evidence that surviving coronavirus may result in immunity from reinfection.
In one of the new studies, researchers infected nine monkeys with Covid-19, the illness caused by the novel coronavirus.
After they recovered, the team exposed the animals to the virus again and they did not get sick.
The scientists, from Harvard University, hope the findings are a positive sign that vaccines under development may succeed.
Dr Dan Barouch, a researcher at the Centre for Virology and Vaccine Research at Harvard’s Beth Israel Deaconness Medical Centre in Boston, whose studies were published in the journal Science, said the findings suggest the animals “do develop natural immunity that protects against re-exposure”.
“It’s very good news,” he added.
Although scientists have assumed antibodies produced in response to the new coronavirus are protective, there has been scant scientifically rigorous evidence to back that up.
Several research teams have released papers – many of them not reviewed by other scientists – suggesting that a vaccine against the virus would be effective in animals.
In the second study, Dr Barouch and his colleagues tested 25 monkeys with six prototype vaccines to see if antibodies produced in response were protective.
They then exposed these monkeys and 10 “control animals” to SARS-CoV-2, the official name of the novel coronavirus.
All of the control animals showed high degrees of virus in their noses and lungs, but the vaccinated animals showed a “substantial degree of protection,” Dr Barouch said.
Eight of the vaccinated animals were completely protected.
These studies, which have been peer reviewed, do not prove that humans develop immunity or how long it might last, but scientists believe they are reassuring.
“These data will be seen as a welcome scientific advance,” said Dr Barouch.
Additional reporting by Reuters
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