Researchers believe understanding how some people naturally resist COVID-19 infection, despite clearly being exposed to the virus. A research team at University College London says some people had a degree of COVID immunity before the pandemic started.
Scientists have been closely monitoring, which included taking regular blood samples, hospital staff during the first wave of the pandemic. The study, published in Nature, highlighted that despite being in a high-risk environment, not everyone came down with COVID-19. It said that around one-in-10 had signs of being exposed, but never had symptoms, never tested positive and never developed COVID-fighting antibodies in their blood.
Part of their immune system was able to get on top of the virus before it managed to take hold – scientists have described this as “abortive infection”. Dr Leo Swadling, one of the researchers, said their immune systems were already poised to fight the new disease. Blood samples showed that the people already had protective T-cells, which recognize and kill cells infected with COVID. The T-cells were able to spot a different part of the virus than the bit most of the current vaccines train the immune system to find.
Dr Swadling explained that vaccines are largely aimed at the spike protein, which covers the outer surface of the COVID virus. “However, these rare T-cells were able to look inside the virus and find the proteins that are necessary for it to replicate. The healthcare workers that were able to control the virus before it was detectable were more likely to have these T-cells that recognize the internal machinery before the start of the pandemic.”
The study pointed out that the internal proteins are very similar in all related species of coronavirus, including the ones that are widespread and cause common cold symptoms. Researchers said targeting these proteins with a vaccine could give some protection against all coronaviruses and new COVID variants.
Prof. Mala Maini believes more could be done. “What we are hoping, by including these T-cells, is that they might be able to protect against infection as well as disease, and we hope they would be better at recognizing new variants that arise.”