New Subvariant 'Most Transmissible' Yet: XBB.1.5 Continues Rise In PA

PENNSYLVANIA — Cases of the new coronavirus subvariant XBB.1.5 continue to proliferate in Pennsylvania, as it has become the region's dominant strain and has been labeled by health experts as the "most transmissible" of the many offshoots of the omicron variant.

The XBB.1.5 variant only made up 6 percent of total cases in the region at the start of December. It now accounts for 32.1 percent, more than any other strain. Pennsylvania's region for this CDC dataset also includes Delaware, the District of Columbia, Maryland, Virginia, and West Virginia, so details are inexact. But it's clear that shape of the virus in the area is changing.

Experts say it is "immune evasive," Fortune reports, although it is not yet clear how effective the new bivalent booster will be in stopping it.

Only about 17.4 percent of eligible Pennsylvanians have gotten their bivalent booster shots. That rate sits at 15 percent nationwide, and includes just 38 percent of older Americans, who are most at risk of a serious illness.

XBB first came on the radar of global health officials in late summer 2022, when it drove up cases overseas in places like Singapore and Bangladesh.

Nationally, XBB was responsible for more than 27 percent of cases last week, up from about 2 percent the first week of December, according to the CDC. The Northeast is where it is most dominant, as up to 70 percent of cases there are believed to be XBB.

“That’s a stunning increase,” White House COVID-19 response coordinator Dr. Ashish K. Jha tweeted last week of the rapid rise in XBB cases, at the same time telling Americans it’s “critical” that Americans are up-to-date on bivalent booster shots.

“For folks without a very recent infection or a bivalent vaccine, you likely have very little protection against infection. And for older folks, diminishing protection against serious illness,” Jha tweeted.

XBB.1.5 combines traits of previous mutations, which health experts say make it spread more easily, even among previously infected or vaccinated people.

It’s more transmissible because of the mutations it has that allow the “virus to adhere to the cell and replicate easily,” Dr. Maria Van Kerkhove, technical lead on COVID-19 for the World Health Organization, told reporters last week.

“The more this virus circulates, the more opportunities it will have to change,”

There is no evidence XBB is more severe than other omicron strains, Van Kerkhove said.

“We are concerned about its growth advantage, in particular in some countries,” Van Kerkhove said, singling out Europe and the Northeast U.S., “where XBB.1.5 has rapidly replaced other circulating variants.”

Overall, still, cases have plummeted in Pennsylvania over the past year, with an average of around 2,000 weekly cases holding steady for months now. Nationally, COVID-19 infections have seen similar precipitious declines, falling from 470,699 weekly cases on Jan. 4, down from last year’s high of more than 5.6 million cases a week on Jan. 19, 2022.

Jha said he’s concerned about XBB, but “Am I worried this represents some huge set back?” he said. “No.”

Besides getting a bivalent vaccine, Jha said Americans should take COVID-19 tests before large gatherings or if they will be seeing someone who is vulnerable. Also, he said, wear high-quality facemasks in crowded indoor spaces, and “work to improve ventilation/filtration in indoor spaces.”

Anyone showing symptoms should get tested right away. The Paxlovid Molnupiravir treatments “should work fine based on what we know,” he said.