Scientists seek to solve the mystery of why some people do not catch Covid | Coronavirus

Scientists seek to solve the mystery of why some people do not catch Covid | Coronavirus

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

In March 2021, she participated in the world’s first Covid-19 challenge attempt, which involved instilling live viruses into her nose and closing her nostrils for several hours in a deliberate attempt to infect her. Yet her body resisted.

“We had several rounds of testing and different testing methods: throat swabs, nasal swabs, other types of swabs that I had never done before as a nasal remover – where you hold a swab in the nose for a minute – as well as blood tests, but I never developed symptoms, never tested positive , “said Garrett. “My mother has always said that our family never gets the flu, and I have wondered if there might be something behind it.”

Most people know someone who has stubborn resisted capturing Covid, despite the fact that everyone around them became ill. Exactly how they do this is still a mystery, but scientists are beginning to find some clues.

The hope is that identification of these mechanisms can lead to the development of drugs that not only protect people from catching Covid, but also prevent them from passing it on.

Garrett is not the only one challenge test participant for having avoided infection. Of the 34 exposed to the virus, 16 did not develop an infection (defined as two consecutive positive PCR tests) – although about half of them transiently tested positive for low levels of the virus, often several days after exposure.

Transmission electron microscope image of Sars-CoV-2 virus.
Transmission electron microscope image of Sars-CoV-2 virus. Photo: Phanie / Alamy

This was possibly a reflection of the fact that the immune system quickly shut down an embryonic infection. “In our previous studies with other viruses, we have seen early immune reactions in the nose that are associated with resisting infection,” said Professor Christopher Chiu at Imperial College London, who led the study. “Together, these results suggest that there is a battle between the virus and the host, which in our ‘uninfected’ participants results in the infection being prevented.”

Some of them also reported some mild symptoms, such as a stuffy nose, sore throat, fatigue or headaches – although as these often occur in everyday life, they may not have been related to virus exposure.

“In any case, the levels of the virus did not climb high enough to trigger detectable levels of antibodies, T cells or inflammatory factors in the blood, which are usually associated with symptoms,” Chiu said.

Other things surveys also suggests that it is possible to shake off Covid in the earliest stages of infection before establishing a proper foothold. For example, during the first wave of the pandemic, Dr. Leo Swadling at University College London and colleagues intensively a group of healthcare workers who were regularly exposed to infected patients but who never tested positive or even developed antibodies. Blood tests showed that about 15% of them had T cells that were reactive with Sars-CoV-2, plus other markers of viral infection.