Test monkeys infected with the novel coronavirus responsible for the Covid-19 pandemic were protected from reinfection for up to 28 days later, AFP reported, quoting a Chinese study in the journal Science.

Scientists from Peking Union Medical College performed an experiment on rhesus macaques, by infecting six of the animals with a dose of the SARS-CoV-2 virus. They developed mild to moderate symptoms, and took about two weeks to recover.

Twenty-eight days after the first infection, four of the six monkeys received another dose of virus, but this time, despite a brief rise in temperature, they showed no sign of reinfection, the study authors wrote.

While the monkeys displayed initial immunity, it's unclear how long such immunity will last in humans — it will be necessary to wait months, or even years, to know if the millions of people infected at the start of the pandemic are protected from re-infection.