Why You May Actually Already Be Safe From COVID, New Study Says

Researchers have discovered preexisting immunity in those who have not yet been exposed.

For the last six months, people all over the world have initiated new measures into their life to try to protect themselves from becoming the next victim of COVID-19. Hand sanitizer has flown off the shelves of stores and masks are seen on most faces when out in public. As scientists and doctors study every facet of the virus, some positive news has emerged. According to a new study, you may actually already be safe from a serious case of COVID. Why? Because some people—even those who have not yet been exposed to the virus—are showing signs of preexisting COVID immunity.

The German study, published in the Nature journal on July 29, looked at a sample of 68 healthy people who had not yet been exposed to the coronavirus. Among those, 35 percent had T cells—a form of immune cells—in their blood, which can directly attack the novel coronavirus.

These T cells were only thought to be found in people who have already had COVID-19, and the study did find those cells in 83 percent of participants who had the virus. But how did those who had not been infected get these immune cells? The study authors believe healthy individuals may have generated these T cells when fighting similar infections from related coronaviruses in the past. And the cells can use "cross-reactivity" to respond to the new coronavirus.

Female doctor consults mature patient during the quarantine for coronavirus

"It does appear in this study that there is a significant proportion of individuals that have this cross-reactive T cell immunity from other coronavirus infections that may have some impact on how they fare with the novel coronavirus," Amesh Adalja, MD, senior scholar at the Johns Hopkins University Center for Health Security, told CNN. "I think the big question is trying to jump from the fact that they have these T cells to understanding what the role of those T cells might be."

This is important considering that the only other major scientific hope for immunity so far has been antibodies, which are proteins formed by a different type of immune cell: B cells. Unfortunately, according to many recent studies, antibodies for SARS-CoV-2 seem to fade exceptionally fast—and may fade as quickly as three weeks, one study from King's College London reported. Though, this isn't too unusual for coronaviruses, as MERS and SARS antibodies faded with time, as well.

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Adalja, who wasn't involved in conducting the study, told CNN that he believes the presence of T cells in non-exposed people may also help to explain why younger adults and children don't often experience severe cases of COVID-19. He says that "one hypothesis" could be that preexisting T cells may be more prevalent and active in younger people than they are in those who are older.

"And if you could compare people maybe with severe and mild illness and try and look at the T cells in those individuals and say, 'Are people who have severe disease less likely to have cross reactive T cells versus people who have mild disease maybe having more cross reactive T cells?' I think that there's biological plausibility to that hypothesis," he said. "It's clear though that the T cell presence doesn't prevent people from getting infected, but does it modulate the severity of infection? That's what it appears could be the case." And for more on fighting the disease, This One Thing Is Fueling the Spread of Coronavirus, Experts Say.

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