EXPLAINER: We have all heard the stories of that one unlucky person we know who has managed to contract COVID-19, not once but twice.
Last month, Newcastle man Will Benson, 20, shared with 9News his nightmarish experience of testing positive to COVID-19 twice in one month.
Overseas, where the first waves of the pandemic saw large numbers of infections, there have been reports which seem even more extreme – of people contracting the virus three or even four times.
For those who have felt on somewhat safer ground because of a previous infection, these reports can seem discouraging, but are reinfections something to worry about?
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How common are reinfections?
As we are increasingly seeing, reinfections do occur with COVID-19.
"If you've had COVID-19, you're certainly not completely protected against getting it again," Dr Deborah Cromer, a senior research fellow at the Kirby Institute's infection analytics program, says.
However, a previous infection, as well as vaccinations and boosters, all play a part in adding to your body's immunity, making the chances of getting severely ill far less likely in subsequent infections.
"If you've been vaccinated and boosted and had the infection then the chance of getting a really severe illness is much lower," Dr Cromer.
"But whether you won't test positive again that's really very different because you may test positive with extremely mild symptoms."
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Dr Cromer sees COVID-19 becoming similar to other respiratory viruses, such as the flu, in terms of reinfection.
"The influenza virus circulates all the time and just because you have had the flu once before in your life doesn't mean you won't get it again," she said.
"But you may not be sick enough to even bother going to see a doctor about it, and no-one would test you and therefore we would never really know whether it was flu or whether it was a cold or some other respiratory virus."
Are reinfections with different variants more likely?
In short, yes.
Contracting a particular variant can help you give you a reasonably strong immunity to that strain of the virus, however, the protection is not as potent for different variants.
"You would definitely be more likely to be infected by a different variant than the same one. But it's not impossible to be reinfected with the same variant," Dr Cromer says.
For the unvaccinated, the risk of getting reinfected both with the same variant or with different ones is higher than for the vaccinated.
"Someone who's unvaccinated would have some immunity, against the same variant but you would be much more likely to be infected with a different variant."
Are reinfections more common in certain variants?
Science is yet to pinpoint a definitive answer, but there are some suggestions that reinfections of the same variant are more common when it comes to Omicron.
Researchers in England from the Imperial College London published a report in December last year estimating the risk of reinfection with the Omicron variant is 5.4 times greater than that of the Delta variant.
"This implies that the protection against reinfection by Omicron afforded by past infection may be as low as 19 percent," the report said.
While there is not yet enough information to say for sure, Dr Cromer said it was logical that reinfections with Omicron could be more common, because the antibodies needed to respond to an Omicron infection are more different to the original COVID-19 virus – for which our vaccines were developed – than for Delta.
Are certain people more vulnerable to reinfection?
Yes, because everyone's immune system is different, as is the amount of antibodies they make in response to vaccinations and natural infections.
"There's a huge spectrum of antibody levels that people produce," Dr Cromer said.
"Some people, for whatever reason, won't have a really good response, and some people will have an amazing response," she said.
Those who produce less antibodies are more likely to get sick and be vulnerable to reinfection.
Immunocompromised people, for example, will have a weaker immune system, perhaps because of an illness or a treatment they are undergoing. Cancer patients are often immunocompromised because of side effects of the disease and the treatments they need to undergo.
Contact reporter Emily McPherson at em********@******om.au.
