As several states lift their COVID-19 restrictions, health experts are warning of a new sub-variant of Omicron called BA.2.

The subvariant has been spotted in 74 countries and 47 U.S. states. Research suggests BA.2 could spread faster and may cause more severe disease, as well as be resistant to some of the current COVID-19 vaccines.

The findings come from new lab experiments in Japan, which health experts emphasize haven't been peer-reviewed.

"We are certainly watching this BA.2 this sub-lineage of Omicron because it is showing some kind of level of transmission advantage,” says Dr. Margaret Harris, of the World Health Organization.

New lab experiments from Japan show that BA.2 may have features that make it as capable of causing serious illness as older variants of COVID-19, including Delta.

Similarly to Omicron, BA.2 appears to largely escape the immunity created by vaccines. A booster shot restores protection, making illness after infection about 74% less likely.

"We certainly don't want it to run rampant, just like we don't want Omicron to run rampant,” Harris says. “We really want countries to step up the vaccination to beat all these variants."

The new research comes as COVID-19 cases and hospitalizations across the U.S. are declining. In New York, the overall positivity rate in the state is at 2.6%. On Long Island, the seven-day positivity rate is at 2.66%. There's been a 40% drop in new cases across New York since last week.

New York will no longer require health care workers to get a COVID-19 booster. State health officials say the decision was made over concerns about staffing shortages and they'll revisit the mandate in three months.

The appearance of BA.2 comes as children are off from school for winter break. Health experts are bracing for uptick in infections when they return.

"Every time you have a vacation, every time family gatherings are coming – people get together without masks, we always see  little surge. We were in the same predicament last year during Thanksgiving with the same amount of numbers right after Delta,” says Dr. Daniel La from AFC Urgent Care.

Gov. Kathy Hochul is expected to make a decision after the winter break about whether to lift the school mask mandate. Health experts say policymakers should err on the side of caution.

"BA.2, Omicron, Delta, Alpha – every time these new variants come out, we have to be careful, you're better being on the safer side than lifting mandates because you see decreasing numbers," says La.