COVID-19 reinfections — what do we know so far?

A molecular bioscientist at the University of Queensland, Dr Larisa Labzin, has helped demystify the topic of COVID-19 reinfections — highlighting what researchers now know for sure, what they think may be true and which areas they still have no idea about.

Dr Labzin highlights that, through genomic sequencing, researchers have now confirmed COVID-19 reinfections to be genuine — not simply original infections that never properly cleared up, as some had initially believed them to be.

“Previously, we weren’t sure if we were seeing bonafide cases of COVID-19 reinfection. It was plausible that people testing positive for the virus, then negative, then positive again, still had remnants of the initial infection inside their bodies,” Dr Labzin said.

“However, the genomic sequencing has shown us that, in these cases, the first and second infections originated from entirely different strains [adaptations] of Sars-CoV-2 [the pathogen that causes COVID-19] — and that the person has been exposed to both strains, respectively.”

What the researchers don’t know, though, is how to predict how sick somebody may get from a COVID-19 reinfection.

“We know that humans can keep a memory immune response, which is why reinfections to most viruses are less severe than an initial infection. In short, the immune system knows how to fight the pathogen better second time around,” Dr Labzin said.

“We expected this to be the same for COVID-19, and that being infected once would make us ‘immune’ from catching — or getting sick from — COVID-19 again.

“This appears to be true for some confirmed cases of COVID-19, but there are also reports of people getting more severe bouts of the virus upon reinfection, and we don’t yet understand exactly why that is.”

From existing knowledge about the immune system, generally, researchers do expect, though, that various factors could be involved.

“When it comes to immunity to reinfection, there are a lot of things at play — individual [genetic] differences, how much virus the person was exposed to in the first and second infection, the duration between each infection and any underlying comorbidities,” Dr Labzin said.

“For example, multiple studies have shown that antibody titres [levels] drop quite quickly over time once you have recovered from coronavirus infection. These antibodies are a major weapon that the immune system uses to fight SARS-CoV-2.

“Additionally, the effectiveness of T-cells, another arm of the immune system, can also vary greatly between individuals,” she added.

Given the uncertainty, Dr Labzin recommends that people continue exercising extreme caution and stringent hygiene practices to minimise exposure to the COVID-19 virus.

“Until we know more about COVID-19 reinfections, people need to recognise the risk and act accordingly — not just for themselves, but for others around them,” Dr Labzin concluded.

Image credit: ©stock.adobe.com/au/Tatyana