The contagious Omicron COVID variant has run rampant through the U.S. this winter. And although the infection spike was sudden and intense, experts say the fact that so many vaccinated people have come down with COVID might help build what some scientists are calling “super immunity.”

Super immunity refers to what happens when a vaccinated COVID patient has a strong immune response following a breakthrough infection, according to a study released in December by researchers at the Oregon Health & Science University. The combination of vaccine immunity and natural immunity—no matter in what order it occurs—gives people more protection than someone who had just one or the other, according to a follow-up OHSU study published at the end of January 2022.

“It makes no difference whether you get infected and then vaccinated, or if you get vaccinated and then a breakthrough infection,” said Fikadu Tafesse, a coauthor of the study and a professor of molecular microbiology and immunology in the OHSU School of Medicine.

That said, the latest OHSU research is based on a fairly small pool of patients—a total of 104 OHSU employees who received the Pfizer vaccine. But the phenomenon of “super immunity” was also recently observed in South Africa, Dr. Jessica Justman, associate professor of medicine in epidemiology at Columbia Mailman School of Public Health, tells Fortune.

In other words, these are still preliminary findings, and many experts are looking for more data before drawing any concrete conclusions. And no one should purposely try to get a COVID infection in an attempt to boost their immunity. “The findings from both studies make sense to me, but it will take more time before we can say they are widely accepted,” Justman says.

Still, it’s helpful that initial studies show that having antibodies from a combination of vaccines and a natural COVID infection offers more protection than simply relying on antibodies generated from multiple, natural COVID infections, according to Dr. Luis Ostrosky, chief of the division of infectious diseases of the McGovern Medical School at the University of Texas Health Science Center at Houston. That’s because the antibodies generated from COVID infections can vary depending on each individual’s immune system.

“The natural infection immunity is robust for some people for some time, but it's not reliably durable,” Ostrosky tells Fortune, adding this immunity generally lasts about three months. And some people never actually gain immunity after their COVID infection.

“We've seen very clearly throughout the pandemic, people who have gotten infected with every single variant because, for some people, immunity never happens, or it's short-lived, and it's not reliable.”

That’s why Ostrosky says most medical experts have always said that vaccination is the best way to achieve immunity. Not only are there likely fewer hospitalizations and deaths, but the hybrid immunity built up through the combination of vaccines and breakthrough cases is proving to be stronger than immunity gained through natural infections.

“Many of us have sort of mixed feelings about what happened with Omicron because obviously, a lot of people are getting infected and just by sheer numbers, many people are in the hospital and dying, but this is building our herd immunity,” Ostrosky says.

Approximately 94% of people must be immune in order to achieve herd immunity and successfully halt transmission, according to the Mayo Clinic. With the stunning number of Omicron cases, health experts believe the U.S. could be on its way to hitting this target, although if that did happen, some experts have said it likely wouldn’t last for long.

A level of herd immunity is important because it can help the U.S. move from the pandemic stage of the COVID outbreak to more of an endemic stage, in which some normalcy returns because most of the population is immune, at least temporarily, from contracting COVID.

Yet when it comes to individuals achieving “super immunity,” it’s important to remember someone has to survive the breakthrough infection, Justman says. That is a real risk, especially for older people and those with medical conditions.

“Even for the majority who survive breakthrough infections, some have a rough time with severe acute symptoms and/or long-haul symptoms,” she adds.

The OHSU study’s authors do believe that this super immunity will be effective against other, future COVID variants, even as the virus continues to mutate. But the level of protection may change as more data emerges.

“I hope it is obvious, but you should not plan to get infected just to get hybrid immunity. It's a very dangerous situation. It is a deadly disease, after all, and there's nothing that guarantees that you do okay, if you get infected on purpose,” Ostrosky says.