Americans who haven’t had covid-19 are now officially in the minority. A study published this week from the US Centers for Disease Control and Prevention (CDC) found that 58% of randomly selected blood samples from adults contained antibodies indicating that they had previously been infected with the virus; among children, that rate was 75%.
What is different about that minority of people that hasn’t yet gotten infected? Stories abound of close calls, of situations where people are sure they could have (or should have) gotten sick, but somehow dodged infection. Not all the questions are answered yet, but the question of what distinguishes the never-covid cohort is a growing area of research even as the US moves “out of the full-blown” pandemic. Here are the possibilities that scientists are considering to explain why some people haven’t contracted the virus.
They behave differently
We’ve seen it play out time and time again—some people adhere more strictly to protocols known to reduce transmission of the virus, including wearing a mask and getting vaccinated. Some people avoid large public settings and may have even been doing so before the pandemic, says Nicholas Pullen, a biology professor at the University of Northern Colorado. Then again, that doesn’t tell the whole story; as Pullen himself notes: “Ironically, I happen to be one of those ‘never COVIDers’ and I teach in huge classrooms!”
They’ve trained their immune systems
The immune system, as any immunologist or allergist can tell you, is complicated. Though vaccination against covid-19 can make symptoms more mild for some people, it can prevent others from contracting the illness altogether.
Growing evidence suggests that there may be other ways that people are protected against the virus even without specific vaccines against it. Some could have previously been infected with other coronaviruses, which may allow their immune systems to remember and fight similarly shaped viruses. Another study suggests that strong defenses in the innate immune system, barriers and other processes that prevent pathogens from infecting a person’s body, may also prevent infection. An innate immune system that’s already not functioning as well due to other medical conditions or lifestyle factors such as sleep or diet may put a person at higher risk of getting sick from a pathogen. There’s not single answer here yet, but initial studies are intriguing and may offer avenues for future treatments for covid-19 and other conditions.
They’re genetically different
In the past, studies have found interesting associations between certain genetic variants and people’s susceptibility to communicable diseases such as HIV, tuberculosis, and the flu. Naturally, researchers wondered if such a variant could exist for covid-19. One June 2021 study that was not peer reviewed found an association between a genetic variant and lower risk of contracting covid-19; another large-scale study, focused on couples in which one person got sick while the other didn’t, kicked off in Oct. 2021. “My speculation is that something will be borne out there, because it has been well observed that resistance embedded in genetic variation is selected in pandemics,” Pullen says. But most experts suspect that even if they are able to identify such a variant with some certainty, it’s likely to be rare.
For now, it’s best for those who haven’t gotten covid to assume they’re as susceptible as anyone else. Whatever the reasons some people haven’t yet gotten sick, the best defense remains staying up to date with vaccinations and avoiding contact with the virus.