More Covid-19 Re-infection Reports After 1st Confirmed Case in Hong Kong

Following a report from University of Hong Kong scientists that a patient has been re-infected with the virus that causes Covid-19, the Erasmus Medical Centre in Rotterdam is confirming that it too has tested and confirmed a case of coronavirus re-infection.

But doctors say the Hong Kong patient's immune system was already seriously compromised.

Hong Kong University's Faculty of Medicine says genetic tests revealed that a 33-year-old man returning to Hong Kong from a trip to Spain in mid-August had a different strain of the coronavirus than the one he'd previously been infected with in March.

The man had mild symptoms the first time and none the second time; his more recent infection was detected through screening and testing at Hong Kong airport.

Dr. Kelvin To from the university's Department of Microbiology says: "Some people might ask will you be immune to the virus forever after you recover? There wasn't a clear answer before, but now it's very clear. After your first infection, there's always a second chance for you to get infected."

The paper has been accepted by the journal Clinical Infectious Diseases but not yet published, and some independent experts are urging caution until full results are available.

Whether people who have had Covid-19 are immune to new infections and for how long are key questions that have implications for vaccine development and decisions about returning to work, school and social activities.

"This is why we have got a lot of research groups actually tracking people, measuring antibodies, trying to understand how long the immune protection lasts – the natural immune protection - and that should be understood as it is not the same as the immune protection that a vaccine provides," says Dr Margaret Harris of the World Health Organization (WHO).

Even if someone can be infected a second time, it's not known whether they have some protection against serious illness, because the immune system generally remembers how to make antibodies against a virus it's seen before.

Professor Francois Balloux the Director of the UCL Genetics Institute says: "It's not bad news. I'd really like to insist on that, the very positive aspect is that this person has been reinfected with a different strain, and as we predicted, all the optimistic people, the optimistic scientists predicted, the second time it led to no symptoms. So the person was not ill, it is actually pretty good news, what would have been bad news is if this person upon infection had been ill, that would have been terrible."

Professor Marion Koopmans, a virologist at the Erasmus Medical Centre associated to Erasmus University says her laboratory has tested and confirmed another case of reinfection.

Koopmans explains: "The hospital that saw the patient and the laboratory that did the diagnosis there, sent the specimens to us and then they asked us, could this be a reinfection because that's what it looked like and we confirmed that it was by genetic sequencing of the virus. And what is also clear is that the person from the first infection really did not have any immune response. So this is a case where the person really is not capable, because of a health condition, of getting a good immune response and then, of course, it's not so surprising that you can be infected again."

She says: "So the big question that is in people's minds is, does this now mean that there is no immunity whatsoever to this virus? I do not think that is the case. I think these are really exceptions that need to be looked at and need to be studied to really understand the full spectrum of this virus and the infection. But my expectation would be, is that they are exceptions."

Koopmans says the patient they tested was elderly and she believes they had strong symptoms of COVID-19 because an existing illness meant their immune system was unable to function effectively.

Both Balloux and Koopmans believe most cases of reinfection will be mild if not asymptomatic.

Balloux says this shouldn't be a great cause for concern.

"This is difficult to say. I don't think we can rule out that this person could have infected someone, but there is increasing evidence that asymptomatic people, people who don't cough, who don't feel any disease are generally less likely to transmit the virus to others than people who are ill," he says.

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