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Scientists say the Covid omicron XBB.1.5 variant is rapidly becoming dominant in the United States because it is highly immunogenic and appears to be more effective at binding to cells than related subvariants.
According to data released Friday by the Centers for Disease Control and Prevention, XBB.1.5 now accounts for about 41% of new cases nationwide in the United States, and the prevalence rate has nearly doubled in the past week. The sub-variant more than doubled as a share of jobs every week through December. 24. Almost doubled from last week’s prevalence rate of 21.7%.
Scientists and public health officials have been closely monitoring the XBB subvariant family for months because the strains contain multiple mutations that can make Covid-19 vaccines, including omicron boosters, less effective and lead to more breakthrough infections.
XBB was first identified in India in August. It quickly became dominant there as well as in Singapore. It has since evolved into a family of subvariants, including XBB.1 and XBB.1.5.
Andrew Pekosz, a virologist at Johns Hopkins University, said that XBB.1.5 is different from its family members because it has an additional mutation that allows it to bind better to cells.
“The virus needs to bind tightly to cells to be more efficient at entering, and that may help the virus become a little more efficient at infecting humans,” Pekosz said.
Yunlong Richard Cao, a scientist and associate professor at Peking University, published data on Twitter on Tuesday showing that XBB.1.5 not only evades protective antibodies as effectively as the XBB.1 variant, but also has higher immune evasion and better binding. cells through a key receptor.
Scientists at Columbia University, In a study published earlier this month in the journal Cellwarned that an increase in subvariants such as XBB “could further weaken the efficacy of current COVID-19 vaccines and result in an increase in breakthrough infections as well as reinfections.”
XBB subvariants are also resistant to Evusheld, the antibody cocktail that many people with weakened immune systems rely on to protect against Covid infection because they do not respond strongly to vaccines.
The scientists described the resistance of the CKD subvariants to antibodies from vaccination and infection as “exciting”. According to the scientists, the XBB subvariants were more effective in protecting against omicron enhancers than the BQ subvariants, which are also highly immune.
Dr. Columbia study author David Ho agreed with other scientists that XBB.1.5 likely has a growth advantage because it binds to cells better than its XBB relatives. Ho also said that XBB.1.5 is as immune evasive as XBB and XBB.1, the two subvariants that have so far been most resistant to infection and vaccine-protective antibodies.
Dr. Anthony Fauci, the outgoing White House chief medical adviser, previously said that XBB subvariants “drastically” reduce the protection the boosters provide against infection.
“You can expect some protection, but not optimal protection,” Fauci told reporters at a White House briefing in November.
Fauci said he was encouraged by the case of Singapore, which has seen a large increase in X-ray infections but has not seen hospitalizations rise at the same rate. Pekosz said XBB.1.5 combined with vacation travel could lead to an increase in cases in the U.S., but he said boosters prevent severe illness.
“It appears that the vaccine, the bivalent booster, provides durable protection against hospitalization with these variants,” Pekosz said. “This really underscores the need to get a booster to a particularly vulnerable population to provide sustained protection against severe disease with these new variants.”
Health officials in the United States have repeatedly urged the elderly, in particular, to be safe they are updated with their vaccinations and treated with the antiviral Paxlovid if they have a breakthrough infection.
