World’s first research finds why some people don’t get Covid

Researchers have shed new light on why some people don’t get Covid-19. In a world first, 36 healthy people who had never had the coronavirus were deliberately given the virus that causes the disease.

The study found that their immune systems responded in a new way, helping to explain how some people avoid getting sick with Covid. The findings may pave the way for treatments and vaccines that mimic these natural defenses, not just for Covid, but potentially for other diseases as well.

It is the first time scientists have been able to see how the body responds to a new disease right from the point of exposure. According to experts, their data can serve as a Rosetta stone for cells that cover different body surfaces and immune cells and reveal early responses associated with protection against infection.

Dr Marko Nikolic, lead author of the study at UCL and honorary consultant in respiratory medicine, said: “These findings shed new light on the crucial early events that either allow the virus to establish itself or clear it quickly before symptoms develop defend. We now have a much better understanding of the full range of immune responses, which could provide a basis for developing potential treatments and vaccines that mimic these natural protective responses.”

The findings, published in Nature, provide the most comprehensive timeline yet of how the body responds to exposure to Covid or any infectious disease. The scientists suggest that it may be possible to extrapolate these findings to other infections, such as influenza, and although the study only looked at Covid, it is very likely that some of the findings will be similar in different infections.

As part of the UK Covid-19 Human Challenge study, led by Imperial College London, 36 healthy people received the virus through the nose. The researchers monitored their blood and nasal mucosa, tracking the entire infection, as well as immune cell activity before the infection event for 16 volunteers.

The teams from the Wellcome Sanger Institute and UCL then used a technology called single-cell sequencing to generate a dataset of more than 600,000 individual cells. In everyone involved in the study, the team discovered previously unreported responses involved in the immediate detection of the virus.

This included activation of specialized immune cells in the blood and a reduction in inflammatory white blood cells that normally engulf and destroy pathogens. People who were able to immediately fight off the virus did not show a typical widespread immune response, but instead generated subtle innate immune responses not seen before, the researchers say.

Dr Rik Lindeboom, co-first author of the study, now at the Netherlands Cancer Institute, said: “This was an incredibly unique opportunity to see what the immune responses look like when we encounter a new pathogen – in adults with no history of Covid-19, in a setting where factors such as the time of infection and comorbidities could be controlled.”

Researchers from the Wellcome Sanger Institute, University College London, Imperial College London, Netherlands Cancer Institute and their collaborators carried out the work as part of the Human Cell Atlas initiative to map every type of cell in the human body.