Test monkeys infected with the novel coronavirus responsible for the COVID-19 pandemic were protected from reinfection for up to 28 days later, a Chinese study out Thursday in the journal Science said.

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.

Scientists from Peking Union Medical College performed an experiment on rhesus macaques, often used because of their similarities to humans, to find out if they have a short-term immunity to the virus.
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Six rhesus macaques were infected in their trachea 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.
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By taking frequent samples the researchers discovered that the peak viral load was reached three days after the monkeys were infected.

The monkeys showed a stronger immune response after the first infection, producing more so-called neutralizing antibodies which may have protected them against short-term reinfection, the scientists wrote.

More experiments are needed to see how long this immune defense remains, the authors said.

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