Two new omicron subvariants have overtaken BA.5 as the prevailing versions of the coronavirus in the U.S.
BA.5 became dominant in July, then consistently accounted for the majority of new Covid infections until last week.
But data from the Centers for Disease Control and Prevention published Friday showed that the new subvariants — called BQ.1.1 and BQ.1 — have taken over. The two together make up around 44% of new Covid infections, whereas BA.5 makes up just 30%.
"BA.5 is essentially declining quickly, probably soon to be gone," said Dr. Dan Barouch, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center in Boston.
BQ.1.1 and BQ.1 cases are also rising in the U.K. and elsewhere in Europe. The two subvariants made up around 18% of new infections in the European Union from Oct. 17-30, and the European CDC expects that share to jump to more than 50% this month or next.
Both of the subvariants are considered part of the BA.5 family — they're sublineages that evolved from BA.5. But preliminary data suggests they are better at evading immunity from Covid vaccines, including the new bivalent boosters, or a previous Covid infection than past versions of omicron. That may give these subvariants higher transmissibility, which could fuel a rise in cases this winter.
Research from Dr. Shan-Lu Liu, co-director of the Viruses and Emerging Pathogens Program at Ohio State University, suggests that BQ.1.1 and BQ.1 both have a mutation that makes them better at entering our cells. Liu's findings are set to be published in the journal Cell Host & Microbe, but a nonpeer-reviewed version is available online.
"There is a clear trend that these two new subvariants are taking off, which is a concern," he said, noting that the share of BQ.1.1 and BQ.1 infections in the U.S. has roughly doubled each week since early October.
Barouch said BQ.1.1 in particular has an additional mutation that could make it slightly better at sidestepping antibodies than BQ.1. For that reason, he anticipates that BQ.1.1 will overtake its sibling and drive "a large amount of infections" this winter.
"BQ.1.1 appears to be the most antibody-evasive variant that we’ve seen to date," Barouch said.
He released preliminary findings this month showing that Covid vaccines (both the original versions and updated boosters) don't hold up as well against BQ.1.1. The data have not been peer reviewed, but the results suggest that people who received updated boosters or original vaccines from Moderna or Pfizer had about seven-fold lower levels of antibodies against BQ.1.1 than against BA.5.
However, because these BQ subvariants are genetically similar to BA.5, vaccines, tests and treatments should still work against them overall, said Andrew Pekosz, a virologist at Johns Hopkins University.
"In the U.S. right now, virtually all the variants circulating are related to BA.5, and therefore if you get the bivalent vaccine, you’ll increase your immunity to it to some extent," Pekosz said.
Scientists don’t expect these new subvariants to cause more severe disease, either.
"It’s encouraging that we’re not seeing really large boosts in hospitalization, because that’s implying that the immunity that we have is still protecting us from severe disease," Pekosz said.
Thus far, Covid symptoms have stayed relatively consistent across omicron variants. Data from the Zoe COVID Symptom Study, which enables people in the U.K. to self-report their symptoms through a smartphone app, suggests that sore throat, congestion, headache, cough and runny nose were the main Covid symptoms as of early November.
"There’s nothing in the signature of the clinical cases that are being reported that suggests that anything is changing in terms of symptoms with these omicron subvariants," Pekosz said.
But the rise of the new subvariants could be a sign that the U.S. is experiencing an increase in Covid cases that isn't reflected in the official data, he added. Many people use at-home tests, but the CDC doesn't track those results unless they're confirmed by a health care provider.
"What we may be seeing here is that there’s probably a lot more infections than we’re counting, and therefore the virus has had a lot more opportunities to mutate," Pekosz said.
He added that it's not yet clear whether BQ.1.1 and BQ.1 will remain dominant for long. Scientists are also keeping an eye on XBB, another omicron subvariant that descended from the BA.2 strain and may be even better than the BQ subvariants at evading antibody protection. XBB is circulating more widely in Asia than the U.S.
With the holidays approaching, some virologists anticipate that the U.S. could see a fresh wave of cases as more people travel and gather indoors.
"Last year around Thanksgiving, omicron came out from nowhere," Liu said. "This is a virus. Anything can happen."