U.S. health officials are tracking a new COVID variant that's a combination of two earlier omicron subvariants.
Known as XBB, this latest subvariant now represents 3.1% of new COVID cases throughout the U.S. and 5% of cases in the Northeast.
Based on preliminary estimates from the U.S. Centers for Disease Control and Prevention, cases of XBB may be doubling every 12 days. However, the variant shouldn't pose the same threat that the emergence of omicron posed a year ago, CBS News reported.
"Where we've seen surges, they've seen mostly it be driven by seasonality, people coming inside, spending more time around one another, but not being specifically being driven by the emergence of a new variant," the CDC's Ian Williams told the agency's emergency response and preparedness advisers earlier this month, CBS News reported
XBB appears to have emerged from the BA.2.10.1 and BA.2.75 omicron subvariants. Along with other omicron sublineages, it appears to be replacing BA.4 and BA.5, subvariants that spread spread widely this past summer. Now, BA.5 is responsible for fewer than 20% of new infections and BA.4 has become almost nonexistent, CDC data shows.
Still, the panic button does not need to be pushed, experts said.
"There has been a rapid rise in XBB, but it doesn't look like it's particularly more severe than other variants," said Derek Smith, director of the Center for Pathogen Evolution at the University of Cambridge, told CBS News late last month.
"XBB, it got our attention and then was prioritized, even though it was small numbers, because it had quite a number of substitutions different from the currently circulating viruses in the [receptor-binding domain], which meant that it might be an escape variant," explained Smith, who helps lead a National Institute of Health's effort to analyze emerging variants.
Luckily, the new COVID boosters may offer some protection against the strain. An early study by vaccine maker Pfizer found the updated booster shots trigger better antibody responses against XBB, but the vaccine does not neutralize this variant as well as prior variants, CBS News reported. That study has not been peer-reviewed yet.
"It doesn't fall off the map, but it goes down. So, you could expect some protection, but not the optimal protection," Dr. Anthony Fauci, the president's chief medical adviser, said Wednesday during a White House briefing, CBS News reported.
COVID hospitalizations are flat or slowing in most regions, and about 75% of Americans live in areas where community levels of infection are "low" by public health standards, CBS News reported.
"However, there's a lot of worry that a new variant could emerge and start us all over again. So, there's a lot of work focusing on making sure we're prepared and thinking about that and watching if it emerges around the world, so we can become prepared," Williams said.