Coronavirus: Infected monkeys were protected from reinfection a month later

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Monkeys infected with the coronavirus that causes Covid-19 were protected from reinfection a month later, signalling that short-term immunity at least may be possible, a new study has found.

The study, by a team from Peking Union Medical College, found that rhesus macaques reinfected with the disease showed "notably enhanced neutralising antibody and immune responses".

The study, published in Science on Thursday, said further research was needed to determine how long this protection would last and how the protection mechanism might work for humans.

Four macaques, a species often used in experiments because of their genetic similarity to humans, were infected with the virus and then reinfected 28 days later.

While the four showed a short increase in temperature, they did not otherwise show any other symptoms or infection.

"Our results suggest that primary Sars-CoV-2 [the official name of the virus] exposure protects against subsequent reinfection in rhesus macaques," the scientists wrote.

"However, it remains necessary to elucidate the protective mechanism against Sars-Cov-2 regarding neutralising antibodies or other immunological roles."

It appeared the primary infection helped to increase the number of antibodies for the virus, which "might have protected the same non-human primates against reinfection in the short term," they said.

While the findings may help scientists researching vaccines, therapies and treatments, the researchers admitted the study had many limitations.

The researchers said the study needed to be repeated over a longer timescale to see how long the protective mechanism lasted, and for monkeys to be exposed to more serious infections than the mild to moderate infections in the Peking Union study.

The scientists noted that there have been concerns that humans could relapse or face reinfection after initial recovery, and cited studies showing that antibodies for the virus have been found in humans 10 to 15 days after infection.

The World Health Organisation in April said that while most studies showed people had antibodies after recovery from Covid-19, some had very low levels of neutralising antibodies in their blood and may not be protected from reinfection.

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This article was first published in South China Morning Post.