According to the Centers for Disease Control and Prevention, 70% of the U.S. population have had COVID-19 at least once, and many have been infected multiple times. But we all know people who have managed to dodge the virus entirely. These so-called  “Novids” or “COVID virgins,” may hold the secret on how to protect ourselves against the virus.

According to NBC News, disease experts are homing in on a few predictive factors beyond behavior, including genetics, T cell immunity, and the effects of inflammatory conditions like allergies and asthma. New York University researchers found that genetics plays a huge role in preventing infection. For example, the genes that inhibit the expression of ACE2 receptors that invite the virus into cells, can be a factor in preventing disease. But to find these genes may be a challenge.

“While there might still be some genetics out there that do render people completely resistant, they’re going to be incredibly hard to find,” says Benjamin tenOever, professor of microbiology at the Icahn School of Medicine at Mount Sinai. “People have already been looking intensely for two years with no actual results.”

In the early days of the pandemic, a community of scientists from around the world set up a global consortium called the COVID Human Genetic Effort, according to WIRED. Their goal is to search for a genetic explanation as to why some people were becoming severely sick with COVID-19 while others had mild cases, or they did not get COVID at all.

In October 2021 the team published the purpose and background for their study on potential genetic links to thwarting COVID in Nature Immunology, and recruited candidates. Andras Spaan, a microbiologist at Rockefeller University in New York, who is part of the group, says the response was “overwhelming.” So far, they’ve had 15,000 applications from all over the world.

Their premise is that some people may have preexisting immunity for COVID-19, just the way genetic mutations confer a natural immunity to HIV, norovirus, and a parasite that causes recurring malaria.

“If you can figure out why somebody cannot get infected, then you can figure out how to prevent people from getting infected,” said another team member, Donald Vinh, of McGill University in Canada. The scientists sorted through the candidates and arrived at 800 to 1,000 individuals who fit their criteria.

Now they will start analyzing every person’s genome to see if they find a pattern to explain the resistance. They will also look for an existing set of genes, such as those that code for ACE2 receptors, the surface proteins on cells that the virus uses to gain entry. Vinh estimates that the process will take four to six months.

Another theory of natural immunity is that some people have T cells that may recognize viruses from past infections like the common cold. The current SARS-CoV-2 is a variation of four other coronaviruses that commonly infect people. These T cells, a type of white blood cell that identifies and fights invaders, seem to recognize SARS-CoV-2 based on past exposure, according to one study.

But while T cell memory probably won’t prevent COVID-19 entirely, it may make the illness less severe, said the study authors. The T cells could clear the virus so quickly from the patients’ bodies that they would not test positive for COVID-19.

Another theory is that people who have asthma or allergies that trigger low-grade inflammation may be protected. That’s why you hear of individuals with a full-blown infection sleeping next to their partner who never get sick. It may be that some people have a higher-than-normal inflammatory response, says tenOever. Another study of nearly 1,400 households found that having a food allergy slashed the risk for COVID in half. Researchers theorize that having a food allergy may reduce the number of ACE2 receptors, thus lowering the risk for infection.