What are the implications of the first case of COVID reinfection?

‘Nothing too surprising. I suspect reinfection is happening a lot more often than we have bothered to find yet. It’ll be happening more frequently in areas where there’s lots of transmission.’
 
That is Associate Professor Ian Mackay, a prominent virologist from the University of Queensland, commenting on a pre-print study, released on 24 August, of the world’s first confirmed case of COVID-19 reinfection.
 
The 33-year-old man first tested positive on 26 March in Hong Kong. He was hospitalised with mild symptoms including cough, sore throat, fever and headache.
 
Then on 15 August – 142 days after the first infection – the man tested positive again, this time during a routine entry screening to Hong Kong airport after having travelled to Spain via the UK. The man was hospitalised again, but remained asymptomatic.
 
The research team from The University of Hong Kong, led by microbiologist Dr Kelvin Kai-Wang To, used genetic testing to analyse viral samples taken from the patient collected 10 days after his symptoms emerged during the first episode, and one day after he was hospitalised the second time.
 
‘It shows that some people do not have lifelong immunity,’ Dr To said. ‘We don’t know how many people can get reinfected. There are probably more out there.’
 
As a result, he said patients with previous COVID-19 infection should continue to comply with epidemiological control measures, such as social distancing and mask-wearing.

Two additional cases of reinfection, one in the Netherlands and another in Belgium, were confirmed by virologists via genetic testing on Tuesday, according to AAP.
 
The prospect of reinfection has been speculated throughout the pandemic so far, with numerous anecdotal reports. But UHK’s pre-print study, accepted for publication in the journal Clinical Infectious Diseases, is the first to confirm reinfection with rigorous testing.
 
The discovery is also in line with recent studies that show antibodies start to wane within around three months.
 
But rather than raise alarm, Associate Professor Mackay says this is a sign of the body functioning effectively.
 
‘That’s what the body does; it makes its initial response, it develops the immune cells, but it doesn’t keep producing antibodies to every single thing or else our blood would be like pea soup – it would be sick with antibodies and proteins,’ he told newsGP.
 
‘So most of the time you’ll develop those antibodies, they’ll go away, but you’re left with the traces of immunity that will fire up again should you ever be challenged by that same virus.’
 
Researchers used genetic sequencing to confirm reinfection, showing infections from two viral strains of SARS-CoV-2 that were ‘clearly different’.
 
Associate Professor Mackay says while viral mutation is common, it can create confusion and anxiety outside of the scientific community.
 
‘In this case, the second infection was a slightly different genetic code to the first. It is still the same virus, it all falls under SARS-CoV-2, but they’re just subtly different,’ he explained.
 
‘A virus is really a cluster of subtly different variants of that virus, and it is constantly changing. So if I was to be infected with SARS-CoV-2, I would have a lot of different variants as they vie for the position to get the next cell and replicate the fastest to then be transmitted.’


Virologist Associate Professor Ian Mackay suspects ‘reinfection is happening a lot more often than we have bothered to find yet’.

With many of the world’s borders closed and travel otherwise significantly restricted, the virologist says such control measures have an impact on a virus’ evolution similar to that of animal species that are living in isolation.
 
‘For example, on an island like the Galapagos you’ll see specific animals that haven’t evolved the same way in other places because they’ve been isolated, while they’ve replicated generations of new offspring,’ Associate Professor Mackay said.
 
‘Viruses are doing the same thing, and each time they produce new offspring they can be subtly tuned to be more adapted to their environment, which might be that person.
 
‘They might have changed some of the things that that person’s immune response attacks so they can escape from it, or they may have found that one of those particular viruses that came in had the ability to replicate a little faster, so it overtook some of the other viruses.
 
‘So you’ve got all this variation going on, and the fittest viruses are the ones that are likely to be coughed or sneezed out at the other end. And then they’ll go on and start the whole process in the next patient.’
 
As is seen in the study, he says scientists have the ability to track each of these changes through genomic sequencing.
 
‘We can sequence the entire 30,000 nucleotides – the library of its life – and see how those changes have occurred from person-to-person first, country-to-country, plane-trip-to-city, whatever it might be – when you compare A to B, you’ll see those differences,’ Associate Professor Mackay said.
 
Could these mutations, however, have implications for the development of a vaccine?
 
If there is significant change in the sequence being used to create the vaccine, it is possible – but unlikely, according to Associate Professor Mackay.
 
‘There’s no sign that that’s been the case here [in Australia], or in any of the work done so far,’ he said.
 
‘It seems like all of the vaccines that are underway do mount the right kind of immune response that will still take out all the different variants of this SARS-CoV-2 wherever it might be, whether it’s a new mutant or whatever.’
 
The fact the man’s second infection was less severe than the first makes the study a case in point.
 
‘This is kind of a way of testing that in this particular case you’ve got two different genetic variants, but it looks like the immunity from the first infection prevented the second infection causing the patient to get ill,’ Associate Professor Mackay said.
 
‘So they were, if you like, vaccinated by the first case and disease was prevented in the second infection.’
 
Professor Nigel McMillan, Director in Infectious Diseases and Immunology at Menzies Health Institute Queensland at Griffith University, says the findings indicate that countries such as Sweden relying on natural herd immunity are ‘on the wrong path’.
 
‘This will not be effective,’ he said.
 
‘Going forward what we need to know is how long T-cell immunity lasts in naturally infected people and, more importantly, how long vaccine responses last as this will determine how often we need to be vaccinated.’
 
Associate Professor Mackay agrees. He believes a vaccine is still the way out of the pandemic for countries with high transmission, as well as others like Australia.
 
‘If we all get vaccinated and we have some immunity develop, then we’ll develop some memory and that means when we get infected a second time, we will hopefully see the same kind of thing that happens here [in the study],’ he said. ‘Which is to say, we could still be infected out in the wild if we all were to meet up with the virus again after we’d been vaccinated, but we wouldn’t get severely sick or we wouldn’t die.
 
‘If it was to produce another kind of immunity that prevented moderate or even mild illness, fantastic.
 
‘But, right now, we just want to prevent that severe disease and death.’
 
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