Why Do Some People Not Catch Covid?

Updated: Apr 8

Phoebe Garrett is a classic example.


Smiley face painted on road above a message saying: Stay Safe

She attended university lectures without catching Covid; she even hosted a party where everyone subsequently tested positive except her. “I think I’ve knowingly been exposed about four times,” the 22-year-old from High Wycombe, England, said.


In March 2021, she participated in the world’s first Covid-19 challenge trial, which involved dripping live virus into her nose and pegging her nostrils shut for several hours, in a deliberate effort to infect her. Still her body resisted.


“We had multiple rounds of tests, and different methods of testing: throat swabs, nose swabs, other types of swabs that I’d never done before like nasal wicks – where you hold a swab in your nose for a minute – as well as blood tests, but I never developed symptoms, never tested positive,” Garrett said. “My mum has always said that our family never gets flu, and I’ve wondered if there’s maybe something behind that.”


Most people know someone who has stubbornly resisted catching Covid, despite everyone around them falling sick. Precisely how they do this remains a mystery, but the good news is that scientists are beginning to find some clues.


One possibility is to do with memory T-cells from previous coronavirus infections – ie those responsible for common colds – that successfully cross-reacted with the new coronavirus and protected them from Covid.


Research in Sweden suggests that immune responses triggered by H1N1 influenza – which was responsible for the 2009-10 swine flu pandemic – and possibly related subsequent strains, may equip people with partial, though not complete, protection against Covid-19.


A third line of enquiry is that a small proportion of people may even be genetically resistant to Covid-19. In October, an international consortium of researchers launched a global hunt to find some of them, in the hope of identifying protective genes. Such resistance is known to exist for other diseases, including HIV, malaria, and norovirus. In these cases, a genetic defect means some people lack a receptor used by the pathogen to enter cells, so they cannot be infected.


It may be that some or all of the above play a role. Or, yet another discovery demonstrates another solution. Either way, the hope is that identifying these mechanisms could lead to the development of drugs that not only protect people from catching Covid, but also prevent them from passing it on. And, possibly, other viruses too.


That would be excellent news. We will keep you posted as we learn of developments.

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