Are COVID-resistant people healthier or is it in their genes?

It could be in their genes, posits Tangye.

“Genetic influences are either making people vulnerable to really severe disease… but may also contribute to resistance… there are populations of people who probably should have been infected and sick but weren’t.”

Exactly which genes have a protective effect is part of an international research project called the COVID Human Genetic Effort, that Christodoulou is involved with.

“We are collecting information and DNA from individuals who have been “hyperexposed” to COVID but who don’t seem to contract COVID – for example, living in a household where multiple family members were infected, but one member of the household wasn’t – to see if genetic factors can be identified that might offer protection against COVID infection,” says Christodoulou, who is also the chair of Genomic Medicine at the University of Melbourne.

While researchers keep searching for the genetic clues, a new study published at the end of April, found booster shots can increase the range of immune cells, called memory B cells, making them more effective at “neutralising” COVID.

With any infection or vaccination, our body responds and then forgets the virus, explains Tangye, but becomes better at responding with repeated exposure. “The first and second doses are like the training, getting your immune system into good shape and ready to take off and the third really gives you the protection… you are primed and ready to go.”

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So if someone who has recently been vaccinated is exposed to COVID, they may be protected. If they have been boosted, this may provide even more protection, at least for a time.

The degree of exposure – how long we were in contact with someone and whether we were inside or out – will also make a difference, as will our behaviour.

“People have become much more cognisant of social distancing and washing their hands and wearing masks. There are those non-pharmaceutical interventions people have embraced,” Tangye says.

As for how healthy you are generally, that unfortunately won’t make us resistant to catching COVID.

“We regularly hear of otherwise young, fit and healthy individuals contracting very severe COVID,” says Christodoulou. “For those otherwise healthy people we know that there are some factors that are associated with this, e.g., having so-called auto-antibodies to type 1 interferons (type 1 interferons are the first line of defence against COVID) or having mutations in genes that are involved in production and function of type 1 interferons.”

“Being healthy is good. But healthy people are still getting sick. It’s not a panacea.”

Interestingly, Tangye adds that there are people who naturally have this type 1 interferon pathway “turned up a little bit”: “That can be pathogenic – they can get these inflammatory diseases that don’t have a defined trigger…these non-infectious, spontaneous flares for no good reason – but people with those conditions may well have some resistance to COVID just because they have that innate immune response primed.”

These people account for only a fraction of never COVIDs. For the rest, it seems to come down to a combination of immunity, genetics, environment and luck.

“Being healthy all round puts you in better shape against infectious diseases and lifestyle disease,” says Tangye. “Being healthy is good. But healthy people are still getting sick. It’s not a panacea.”

Most of us may not be able to do much to avoid the virus, but we can still look to never COVIDs for some answers.

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“If we can identify genetic reasons why people don’t get COVID, it may help inform ways by which SARS COV2 enters or attacks our cells – remember viruses are hopeless on their own. They need all the machinery of our cells to be disease-causing,” explains Tangye. “So if we can disrupt the ‘human cell processes’ without too many adverse events we could be better at stopping viral infection.”

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