Can you catch COVID twice? Or are you immune?

Central Coast resident Mitch Rogers has just come out of two weeks of complete isolation, which he says was “pretty tough”.

After contracting COVID early this year, the 32-year-old, who lives by himself, retreated to his Umina Beach home to ride out the symptoms. They ended up taking 14 days to subside, double the mandated seven day isolation period.

But as he re-entered the world on Monday, returning to his job in the care sector, he was far from relieved. “I feel more cautious and nervous,” he says.

Partly, he’s worried that he could still be infectious and unwittingly pass the virus to someone else. (He thinks he caught the virus from someone who had recently left isolation and thought they were clear.)

But mainly, he’s afraid to get sick again.

“The booster talk is confusing, some sources say you’re meant to be immune for six months, some say six weeks,” he says.

“I went to a takeaway place and I was the only person wearing a mask. I couldn’t remember if the rules changed, but I didn’t feel safe not wearing one.”

More than a million Australians have now had COVID, and while many who have recently contracted the virus describe it as a weight off their shoulders, for others like Mitch, the anxiety has continued. 

So, does a COVID-19 infection mean you won’t get it again? And how careful should you be when you leave isolation? Here’s what the experts say.

I’ve recently recovered from COVID. Can I get it again?

Yes, but probably not for a little while.

That’s because infections, like vaccinations, help your body create antibodies that fend off SARS-CoV-2 — the virus that causes COVID-19. This immunity is most powerful immediately following an illness, when the cellular memory of the infection and neutralising antibodies are at their strongest.

“Someone who has been vaccinated previously and then gets an Omicron infection effectively gets their immunity ‘boosted’ by infection in a similar way to a third dose of vaccine,” says Professor Miles Davenport, who leads the Kirby Institute’s Infection Analytics Program.

“The expectation is that this ‘boost’ to immunity should provide high levels of protection from Omicron infection for a significant period, likely up to 12 months.”

Experts estimate Omicron currently accounts for upwards of 90 per cent of COVID-19 cases nationwide. But due to the influx of cases and delays with genomic testing, many people won’t know whether they have contracted Omicron or the earlier, and more dangerous, Delta strain.

“Infection with one variant generally provides a degree of protection from other variants,” Professor Davenport says. “Therefore, infection with Omicron will provide the strongest protection against [reinfection with] Omicron — but also weaker protection against other variants.”

Recent research from South Africa suggests people who have recovered from Omicron may be better placed to stop a Delta infection. The study of 15 participants who had recently become infected with Omicron, led by the Africa Health Research Institute, found the participant’s ability to neutralise the Delta variant increased more than fourfold. The results have not yet been peer-reviewed.

The same, however, does not appear to be true in reverse, with Omicron able to more easily evade immunity from other variants. But even so, epidemiologist Mary-Louise McLaws, who advises the World Health Organization on COVID-19, says it’s quite safe to assume you won’t be reinfected with any variant within three months of recovery.

This is because neutralising antibodies are at their highest during that period, before beginning to wane. “With Omicron and Delta, we’re probably not going to have our antibodies forever,” she says. 

How long will the protection last?

That’s up for debate, and will likely differ from person to person. Like Professor McLaws, Professor Steven Tong, an infectious disease physician from the Doherty Institute, estimates people who have recently recovered from Omicron should “have a pretty high level of protection” for at least three months.

“It’s too soon with Omicron, we don’t really know,” Professor Tong says. “While I can speculate that I think you’ll have some protection, we don’t know that for sure.”

In New South Wales, health authorities are playing it safe. While there is an exemption in place meaning people who have recently recovered from the virus do not have to isolate if they are a close contact, this only applies to people who have had the virus in the past month.

“People who have recovered from COVID-19 have a low risk of getting it again in the 28 days after you are released as most people develop some immunity,” the NSW Health website reads.

But a bigger issue is whether another variant that’s able to evade pre-existing antibodies, like Omicron, will come along. And if so, when?

“We don’t know what will happen in six months time,” Professor Tong says.

“People that have been infected with Omicron, you can’t say whether they could be reinfected with another variant or not — but theoretically it’s possible.”

What about boosters?

Despite any previous COVID infection, you still need to get the booster.

But the spike in infection numbers has unfortunately coincided with the rush of vaccine appointments for kids and booster eligibility for adults, creating a logistical nightmare for organising bookings.

While you shouldn’t go to a vaccination appointment if you have COVID-19 or symptoms, experts are still urging people to get their booster shot as soon as they are able. But when is the best time?

Federal health advice is unclear: while it says vaccination can be delayed by up to six months following an infection, due to a reduced chance of reinfection in this time, it also advises that there is no requirement to do this

Professor McLaws recommends waiting three months after an infection to get a booster — assuming you are feeling well — because that’s when your neutralising antibodies will start to wane. Professor Tong, however, says the sooner the better.

“If you’ve recovered from your acute illness, let’s say you’re two or three weeks down the track and you’re back to normal, then that’s a good time to have your third shot,” he says. 

He stresses that even people who have recovered from the virus should still get whatever vaccine shot they are eligible for, as it will help protect against reinfection and hospitalisation down the line. 

“It does appear, at least with previous variants, that a previous infection and then vaccination on top of that, really does give you almost super immunity against COVID.”

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