- Three years after the novel coronavirus emerged, a new variant, XBB.1.5, is quickly becoming the dominant strain.
- A potent mix of mutations makes it easier to spread broadly.
- It includes those who have been previously infected or vaccinated.
XBB.1.5, pegged by the World Health Organization as “the most transmissible” descendant yet of the omicron variant, rose from barely 2 percent of U.S. cases at the start of December to more than 27 percent the first week of January, according to new estimates by the Centers for Disease Control and Prevention.
Most Transmissible Descendant
While there is no evidence so far that XBB.1.5 is more virulent than its predecessors, a recent swirl of misinformation linking the rise of new variants to vaccination has cast a spotlight on this latest strain. “XBB did not evolve because people were vaccinated,” said Vaughn Cooper, a professor of evolutionary biology at the University of Pittsburgh. “The way it evolved, let’s be straight, is because people were infected by multiple viruses at the same time.” Virologists who studied XBB.1.5 say it does not appear better at escaping antibodies than other immune-evading predecessors, but it is better at binding to the cell and replicating.
Health officials are urging Americans to get a booster dose of the new coronavirus vaccine formulated for omicron sub variants to protect against an expected winter surge in cases. XBB prompted some concerns because lab studies showing antibodies generated by vaccines struggle to block that variant. But that doesn’t mean the vaccines don’t work: For much of the past year, waves of infections from immune-evading variants have not caused surges of severe illness at hospitals, and experts believe that widespread immunity from shots and prior infections are making people more resilient to the virus.
While antibodies do not provide foolproof shields against reinfections, they still reduce the odds of contracting the virus and greatly reduce the likelihood of severe illness and hospitalization. But the focus on boosters is also drawing criticism. An opinion piece published in the Wall Street Journal by a member of its editorial board suggested that repeated vaccination made Americans more susceptible to new variants.
“Raising doubts about the value of vaccines will continue to lead well-intended people to delay getting an updated vaccine, leading to a clearly documented risk of death or severe illness,” FDA commissioner Robert Califf tweeted. Several studies have tried to examine whether SARS-CoV-2 variants spread faster in locations with higher vaccination rates and found no evidence to support it.
While XBB.1.5’s mutations have sparked scientific intrigue, experts caution it doesn’t substantially change circumstances for ordinary people navigating pandemic life with omicron’s descendants as the dominant strains since last spring. In addition to staying up to date on boosters, don’t assume you can’t get sick again if your last shot or bout with covid was more than several months ago.
XBB.1.5 surged first in the Northeast, where it now makes up nearly three quarters of cases. But hospitals there have not raised alarms about people coming in sicker because of the new subvariant. Experts hope hospitals in other parts of the country can share Northwell’s experience: weathering a rise of cases without covid wards packed with people fighting for their lives.
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