As the Virus Evolves, COVID-19 Reinfections Are Going to Keep Happening

After the Omicron variant caused massive numbers of infections this past winter, lots of people looked on the bright side, hoping it would be “a free shot for the country,” says Eli Rosenberg, deputy director for science at the New York State Department of Health’s Office of Public Health. Even though lots of people got infected with the highly contagious variant, at least they would then have immunity against the virus, protecting them from getting sick in the future. In theory.

But that hasn’t turned out to be true. Many people—even those who are vaccinated, boosted, and previously infected—are again testing positive as Omicron relatives like BA.2 and BA.2.12.1 circulate throughout the country.

Not all states track reinfections, but many of those that do are seeing upticks. In Indiana, about 14% of cases reported in the week ending May 12 were reinfections, up from about 10% the week before. North Carolina and New York are seeing similar, albeit slightly lower, percentages. The actual numbers may be higher, since official case counts are increasingly missing diagnoses due to widespread home testing and other factors.

“This is going to keep cycling through the population,” Rosenberg says. “Every few months you could keep getting it.”

Unlike viruses like measles, which strike once and leave behind lifelong immunity, SARS-CoV-2 has proven that it’s capable of reinfecting people since at least the summer of 2020. The U.S. Centers for Disease Control and Prevention recently warned that people who have had COVID-19—around 60% of the U.S. population, by the agency’s estimates—should not assume they won’t get sick again.

Both COVID-19 vaccinations and prior disease provide some protection against future illnesses, but they’re better at preventing severe disease than infection, says Dr. Rachel Presti, medical director of the Infectious Disease Clinical Research Unit at the Washington University School of Medicine in St. Louis. Reinfections are likely to be mild, she says, but they’re also probably going to keep happening.

“When you have immunity, it’s protecting you when you get sick. It doesn’t really protect you from getting infected,” Presti says. “It’s not like an external wall. It’s more like guards inside the gates.”

Rosenberg says there’s always a spike in reinfections when a new variant starts to surge, since antibodies from one strain may not hold up well against the next. Experts often say reinfection is unlikely for at least 90 days following a COVID-19 illness, and maybe longer. But that’s only true if a new variant doesn’t pop up, Rosenberg says, and the virus “keeps switching on us every few months—faster than 90 days.”

Research suggests the newer variants are also better at evading immune defenses than their predecessors. Omicron caused huge numbers of breakthrough infections and reinfections thanks to mutations that made it extra contagious and able to get around natural immune blockades, research shows.

It’s too early to say exactly how BA.2.12.1 will compare. But two studies published in May as preprints—meaning they were not peer-reviewed prior to publication—suggest that newer Omicron subvariants, including BA.2.12.1, could be even better at evading prior immunity than the original Omicron strains.

It’s early, but preliminary findings suggest “it’s both very highly transmissible and it has escape mutations…that make it somewhat resistant to previous infection or to vaccination,” says Dr. Peter Hotez, co-director of the Center for Vaccine Development at Texas Children’s Hospital and dean of the National School of Tropical Medicine at Baylor College of Medicine.

Presti says BA.2.12.1 has so far caused more reinfections than she would have expected, given how similar it is to the original Omicron strain that infected huge swaths of the U.S. population. “Particularly [with] people who were vaccinated and then got Omicron, it surprises me that they’re getting sick again,” she says.

The good news is that vaccines and prior infections still seem to be effective at preventing serious disease. People with immunity from vaccination and past bouts with the virus are better protected than those who have been infected alone, Hotez says, so everyone should stay up-to-date on their shots. Combined with “situational awareness”—like wearing a protective mask or skipping large, mask-free gatherings if COVID-19 is rampant in your area—Hotez says that’s our best defense, at least right now. (Other tools, such as nasal vaccines that could theoretically stop transmission, boosters that could protect against multiple variants, or protein-based shots that could provide more durable protection, are in the works, but they’re not here yet.)

The big question is what the virus will do in the future. Presti says it’s starting to look like it may one day resemble regular coronaviruses, such as those that cause the common cold. People can catch the common cold multiple times in one year, but it rarely causes serious illness.

But there’s a long way to go before COVID-19 is truly comparable to a cold, Presti says. Thousands of people with COVID-19 are admitted to U.S. hospitals every day, and hundreds of people die from it daily. The virus can be especially serious for people who are unvaccinated, immunocompromised, or have underlying medical conditions, but even fully vaccinated people who experience fairly mild cases can develop complications like Long COVID, an often-debilitating condition that can linger for years after an infection.

No one knows for sure whether SARS-CoV-2 will ever cause illnesses as mild as the common cold. The virus is continually evolving, and it’s impossible to predict what the next variant will bring—but it’s safe to assume reinfections are no longer the rarities they were once thought to be.