Omicron Reinfection: If You Already Had Omicron, Can You Still Catch BA.2?

Omicron subvariant BA.2 is now estimated to be the dominant COVID-19 strain in the country, according to the Centers for Disease Control (CDC). Experts fear the emergence and rapid spread of the subvariant may cause another surge in COVID-19 cases.

However, preliminary data currently suggest that if you were infected with Omicron's BA.1 variant, you may have strong protection against reinfection with BA.2.

A preprint study posted to medRxiv assessed 187 cases of COVID-19 between November 22, 2021, until February 11, 2022 reinfection and found 47 instances where BA.2 reinfection occurred after an initial Omicron infection. Their findings show that reinfections can still occur, but it’s relatively rare.

While the study has yet to be peer-reviewed—therefore it should not be used to guide clinical practice—it demonstrates that some people who got COVID-19 in the last Omicron surge may have some protection against reinfection.

Previous Infection Provides Some Protection

The BA.1 Omicron variant and BA.2 share multiple common mutations. Because of the relative genetic similarity, it is considered a subvariant of Omicron instead of a completely new variant altogether, though BA.2 likely has a selective advantage over the other. The BA.2 subvariant has several mutations that make it different from Omicron, many of which appear to make it more contagious, Mark Loafman, MD, MPH, family physician at Cook County Health, told Verywell.

“However, BA.2 still has many of the immunogenic features of BA.1 in terms of both vaccine-induced and naturally acquired immunity, and fortunately, this subvariant still responds to almost all of the treatment options we have available for COVID-19,” Loafman said.

Recovering from a COVID-19 infection can provide individuals with natural immunity against COVID-19. Previous infection with Omicron, in particular, may provide strong protection against infection with BA.2. 

“There is much overlap between BA.1 and BA.2, so cross-protection is to be expected,” Stanley H. Weiss, MD, professor of medicine at the Rutgers New Jersey Medical School and professor of biostatistics and epidemiology at the Rutgers School of Public Health, told Verywell. “But it won’t be complete. Some persons do not mount a robust immune response, so some breakthrough infections are to be expected.”

The pre-print study is the first to provide useful quantitative data on reinfection rates, and the age distribution was particularly interesting, Weiss said. The authors found that none of the reinfection cases occurred among patients older than 38 years old, and 70% were among patients under the age of 20.

“This reflects in part the very different epidemiology of Omicron compared to prior variants, and the much lower rate of vaccinations in youth,” he added.

Reinfection Risk for Unvaccinated Versus Vaccinated

The best protection against COVID-19 reinfection is to get vaccinated and boosted as soon as you are eligible. The mRNA vaccines provide longer, stronger immunity than natural infection, especially for individuals who have had their booster shot, Loafman said. The preprint study also found that 89% of the reinfection cases with BA.2 occurred among unvaccinated individuals.

“The reinfection risk—for someone who has had BA.1, to then get BA.2—is likely to be much higher among the never-vaccinated,” Weiss said. “Due to the broadening of immunity seen among those who had been vaccinated before getting a breakthrough infection with BA.1, [the risk is] expected to be diminished among those vaccinated, with lessening risk as we proceed from one to two to three doses.”

Recently, the Food and Drug Administration (FDA) authorized a second mRNA booster shot for immunocompromised individuals aged 12 years and older and for people aged 50 and older four months after their initial booster shot. Given the evidence of waning protection, the second booster shot is intended to increase immunity against COVID-19.

Vaccination increases not only the protection against reinfection but also its severe outcomes, experts said.

“Reinfection for those who are not fully vaccinated against COVID-19—which means boosted when indicated—poses a far more serious health risk,” Loafman said. “Most hospitalizations and serious illness continue to be among the unvaccinated and those who are not fully vaccinated and boosted against COVID-19.”

Is Another Surge Coming?

The emergence of BA.2 should not be so easily dismissed. Even if natural and vaccine-induced immunity conferred some protection against the disease, it’s necessary to remain cautious.

“BA.2 highlights that the COVID pandemic is really not over yet, as much as we all fervently hope it would have been by now,” Weiss said. In some countries where many are unvaccinated under the false belief that they no longer have to worry about COVID-19, there are high rates of infection, morbidity, and mortality, he added.

The number of BA.2 infections has been steadily increasing over the past few weeks. Based on what we are seeing in other countries, another surge in the U.S. is possible, Loafman said.

“The severity of the surge caused by the BA.2 subvariant will depend on the factors we know have influence on the COVID-19 pandemic, including weather, vaccination and booster rates, voluntary use of isolation when ill, and the use of masking and social distancing in both crowded and indoor settings,” he added. “Given these variables, we are likely to see wide regional variations in how this surge will play out.”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.