The re-infection was found in a 33-year-old man in Hong Kong after he was screened at a Hong Kong airport having returned from Spain. The man had already been infected with the virus roughly four months prior, and had been admitted to hospital with symptoms including fever, cough, sore throat and headache.
He then recovered and was discharged in mid-April, before becoming re-infected this month.
The man did not show any symptoms at all the second time around, which is a sign his immune system had helped protect him to some extent, Science News reports.
Professor Gordon Dougan, an expert in vaccinology and immunology at the University of Cambridge’s Cambridge Infectious Diseases research centre, told Express.co.uk the implications news of the reinfection might have.
He said the first confirmed report of a COVID-19 reinfection is “not entirely unexpected,” adding two other confirmations from Holland had followed soon after.
Professor Dougan told Express.co.uk: “We know from human volunteer challenge studies carried out in the UK in the 1980s that other coronaviruses e.g. those that cause common colds, can re-infect.
“It looks as if people do become immune to COVID-19 but the question is for how long? Normally any immunity starts to wane after an infection.
“Immunity can last for a few months but in some cases e.g. chickenpox, it normally lasts a lifetime.
“It looks as if the person in Hong Kong was re-infected but asymptomatically. This is likely because they still had some immunity and although the virus could get into the nose it could not cause disease.
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In any case, it is not certain how any of this could impact a vaccine going forward.
Professor Dougan explained it might not matter, since immunity granted by vaccines is different than immunity from a natural infection.
According to Science News, vaccines could “trigger a more robust immune response” and help grant herd immunity.
A study describing the findings of the first confirmed re-infection has been accepted for publication in Clinical Infectious Diseases.
Throughout the pandemic, there have been stories of people catching the virus more than once.
However, these reports did not come with any genetic evidence that both the first and second infections had been caused by two different viruses.
In the Hong Kong case, it was determined the man in question had been infected by two versions of COVID-19 each time.
Science News adds one version was circulating in the UK and US in March and April, while the other was linked to Switzerland and the UK in July and August.