A small number of people exposed to COVID-19 early in the pandemic resisted infection naturally, according to a new British study, potentially offering new insight to develop even more effective vaccines.
Researchers at University College London identified proteins in the virus that were recognized by protective T-cells, which kill COVID-infected cells, in a study of 731 healthcare workers in two London hospitals during the first wave. About 10 percent of the workers showed signs of exposure to the virus but never had symptoms, never tested positive and never developed antibodies that fight the virus.
Somehow, their immune system was prepared for this unknown virus, eliminating it in what’s known as an abortive infection. Blood samples revealed the T-cells, which would have been part of their immune response even before the pandemic began. The results were published in the journal Nature.
COVID-19 vaccines target the spike protein, which allow the virus to penetrate host cells and cause the infection. T-cells, meanwhile, find the proteins within the virus needed for it to replicate. It’s these replication proteins — they are less likely to change with each mutation of the virus — that interest scientists. That could mean people who resisted COVID-19 might have been exposed to other coronaviruses.
But T-cells, say researchers, aren’t necessarily enough to offer full protection against the virus. The study did not examine whether any of the participants who initially resisted the virus retained protection when exposed again.
But the human body recognized this new virus even before some humans did. And others became ill without knowing it was COVID-19, adding uncertainty to when the virus actually arrived in this country.
“That’s such a hard question,” says Dr. Steven Valassis, Chair of Emergency Medicine at St. Vincent’s Medical Center in Bridgeport. “We all know people who had upper respiratory infections in those preceding months and a lot of them said, ‘I wonder if that was COVID?’ Some got antibody tested and they may have been positive. But it doesn’t prove that (particular) infection was really COVID because they might have had COVID later.”