Ever since the pandemic began, some people have gotten sick many times with Covid-19 while others have avoided it completely despite being in close contact with those who tested positive.
A professor of comparative immunology and biochemistry at Trinity College Dublin, Dr Cliona O'Farrelly spoke on RTE’s Claire Byrne Live radio show to explain why this could happen.
She gives 4 reasons, including socio-economic backgrounds, good overall health and careful behaviour.
Another reason she gives is innate immune response signature, something that is currently being studied to see if certain people are resistant to the virus.
Dr O'Farrelly explained: "How people live has got a lot to do with their circumstances and then on top of that then is this percentage of people who have what we would call an innate immune signature, that's what we're looking for"
“So I think those four things are really important; your socio-economic status, your general health well-being, how you behave and then this innate resistance."
She and the team at Trinity have been studying a group of women who contracted Hepatitis C through blood transplants while others were naturally protected.
She believes that this could be down to the innate immune response, just like Covid-19.
"We do have data now that the women who did not become infected had a more innate immune response, that's an immune response that kicks in immediately on encountering the virus and it is the part of the immune system that is right at the site of where the virus is."
“Flu is a totally different type of virus. The viruses come from very different families and just because you’re resistant to one does not necessarily mean you’re resistant to the other.
“But, this is what we would be wanting to research.”
The experts are looking into Covid-19 resistance by studying people from 40 different countries who didn’t get the virus despite being in close contact.
Dr O'Farrelly said: "Ideally we are looking for people who have resisted the virus twice, during the first wave and more recently with the Omicron and ideally we need people whose partner was PCR positive while they shared a room with them and they remained PCR negative."