CDC estimates new Omicron version accounts for 20 percent of New England COVID-19 cases

A new version of the Omicron coronavirus variant accounts for 20 percent of COVID-19 cases in New England.Barry Chin/Globe Staff/file

A new version of the Omicron coronavirus variant now accounts for 20 percent of COVID-19 cases in New England, the Centers for Disease Control and Prevention estimated Tuesday. But experts say it’s too soon to tell what the impact will be.

The new subvariant, BA.2.12.1, was in the news after it was spotted along with another new subvariant in New York and blamed last week by officials there for pushing up cases in the central part of the state.

The original Omicron variant BA.1 caused a terrifying surge that peaked early this year in the United States. Cases have plummeted since then, though they recently turned up again as the more contagious BA.2 subvariant has arrived.

BA.2 still accounted for 75.6 percent of cases in New England as of Saturday, according to CDC estimates. (The CDC included the other subvariant detected in New York, BA.2.12, in the BA.2 count.)

But BA.2.12.1, which experts say appears to be even more contagious, has been coming on strong. It has accounted for a rapidly growing share of cases, rising from 1.5 percent on March 19 to 20 percent on Saturday.

Nationally, BA.2.12.1 is estimated to account for 19 percent of cases as of Saturday.

The emergence of more new subvariants is the latest curveball thrown by an unpredictable virus.

“We are seeing increasing cases of BA.2.12.1 as well as multiple additional Omicron sub-variants. These Omicron sub-variants have generally proven more transmissible than the original Omicron BA.1 variant, but so far they have not resulted in more severe disease and have not escaped vaccines more than BA.1. However, data with BA.2.12.1 is still largely pending,” Dr. Dan Barouch, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center, said in an e-mail.

Virologist Dr. Jeremy Luban at UMass Chan Medical School told NPR last week that he was “relatively optimistic” the vaccines will continue to protect against BA.2.12.1. “So people who have been vaccinated and boosted are not going to be hospitalized, by and large, unless there’s some extenuating circumstances.”

Scientists are also keeping a close eye on the Omicron XE subvariant as well as subvariants BA.4 and BA.5.

Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, recently told The Washington Post scientists do not yet understand why so many subvariants of Omicron have emerged in recent months.

The Massachusetts Department of Public Health said Tuesday it did not have an estimate of how many Massachusetts cases are currently being caused by BA.2.12.1, but it emphasized in a statement the same things that have worked in the past to prevent COVID-19 continue to work.

“The public health guidance has not changed, and we know what to do to protect ourselves from COVID-19 and its variants,” the department said in a statement. “As we adjust to life with COVID-19, Massachusetts has the tools in our toolbox to manage the virus and its variants.”

The officials urged people to get vaccinated and boosted, get tested, and, if the test is positive, talk to their doctors about treatments available for people who have mild to moderate symptoms.

Material from Globe wire services was used in this report.