While BA.5 continues to dominate the U.S. COVID-19 cases, health officials are keeping an eye on another Omicron subvariant, called BA.2.75.
Some Twitter users and media reports have unofficially called BA.2.75 “Centaurus” after a Twitter user dubbed it as such.
BA.2.75 was first detected in India in May. Since then, 23 countries and 10 U.S. states have recorded cases of the variant. But cases remain rare—BA.2.75 is responsible for fewer than 0.5% of U.S. cases.
The World Health Organization (WHO) is keeping an eye on the variant, but it’s too early to know whether the variant can spread or cause more severe disease than other variants.
Omicron BA.5 and its sister, BA.4, quickly overtook the prior Omicron variants because they contained mutations that allowed them to infect and spread more easily. Both subvariants now account for more than 93% of the U.S. COVID cases.
The new variant is an offshoot of BA.2, the Omicron variant that drove the recent winter COVID-19 surge. BA.4 and BA.5—the sister variants which are responsible for the vast majority of cases now—also stem from BA.2.
The WHO is tracking BA.2.75 as an Omicron subvariant “under monitoring.” If there’s enough evidence that the variant is different enough from other variants, it may get labeled as “variant of concern.”
Each Omicron variant expresses different mutations in the spike protein on the outside of the virus. The neutralizing antibodies induced by vaccination, monoclonal antibodies, and natural infection glom onto the spike to prevent it from infecting cells. When the spike protein changes, these antibodies have a harder time recognizing the virus and neutralizing it.
Scientists have noted nine mutational differences from BA.2 in the spike protein and five outside that region.
It’s too soon to know just how those mutations will impact the disease course for someone infected with it. Ultimately, the number of mutations is not as important as the disease outcomes for those who get sick with it, said Waleed Javaid, MD, FACP, an epidemiologist and director of Infection Prevention and Control at Mount Sinai Downtown Network.
There’s little real-world data about how well the variant can escape immunity from vaccination and prior infection. And it’s not yet clear just how transmissible it is compared to other variants.
But some early lab studies give clues about how BA.2.75 may compare with other Omicron variants.
In a couple pre-print studies from July, researchers tested how well the variant is neutralized by the immune cells in the blood of people who had been vaccinated, and those who recovered from BA.1 and BA.2. In these early analyses, it seems that BA.2.75 was no better at slipping by these antibodies than was BA.5.
They also found that the monoclonal antibody bebtelovimab, which is the only therapy that appears to prevent death in patients hospitalized with Omicron, is pretty responsive to BA.2.75, too.
Another group of researchers tested BA.2.75’s spike protein in a sample of blood from those who had been vaccinated and recovered from Delta infection. The variant appeared to slip by the antibodies in these samples easier than BA.4 and BA.5 did. The Delta wave hit India hard, meaning many people there likely have some exposure to Delta. This could help explain why BA.2.75 is gaining ground on BA.4 and BA.5 there.
Since most of the available data comes from India, it’s not yet clear how well the variant will compete at a global level. And only time will tell whether it contends with BA.5 in the U.S.
“Guessing these things is a little bit difficult. To say ‘this mutation will worsen this pandemic’ is not something we can easily say,” Javaid told Verywell. “We have to wait, watch, and see.”
Many people in the U.S. have some degree of immunity against COVID-19. More than 70% of people eligible for vaccination in the U.S. are fully vaccinated and some 44% may have recovered from natural infection. A new, more transmissible variant may not necessarily cause a surge in hospitalizations and deaths given this population immunity.
Still, only about a third of Americans are fully vaccinated with a first booster shot. An even smaller portion has gotten their second booster dose.
Studies indicate that a third dose of COVID-19 vaccine boosts immunity to Omicron variants 20-fold compared to a two-dose regimen. A fourth dose for those older than 50 years further bolsters the immune system.
Ultimately, the protective measures that experts have long touted—vaccination, mask-wearing, and good hygiene—continue to be the best ways to prevent COVID-19 sickness.
More COVID-19 variants are likely to evolve in the coming months.
“Hopefully the lethality of the virus will kind of start to go down to a point that will be nothing more than a common cold,” Javaid said.
In the meantime, he emphasized the need to take protective measures, regardless of the variants at hand. And with the recent authorization of Novavax’s COVID-19 vaccine, there are even more vaccine platform options for those who haven’t yet received the shot.
“I still see people who are unvaccinated going to the hospital, going to ICU, and dying. It hurts to see that,” Javaid said.
The best way to protect yourself against BA.2.75, and all COVID-19 variants, is to be fully vaccinated and receive a booster shot. People who are 50 years or older should also get a second booster dose.
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