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The Covid omicron XBB.1.5 variant is rapidly becoming dominant in the US because it is highly immune and appears more effective at binding to cells than related subvariants, scientists say.
XBB.1.5 now accounts for about 41% of new cases nationwide in the US, nearly doubling its prevalence over the past week, according to data released Friday by the Centers for Disease Control and Prevention. . The subvariant more than doubled as part of cases every week through December 1. 24. In the last week, it almost doubled from 21.7% prevalence.
Scientists and public health officials have been closely monitoring the XBB family of subvariants for months because the strains have many mutations that could make Covid-19 vaccines, including omicron boosters, less effective and cause infections. even more important.
XBB was first identified in India in August. It quickly became dominant there, as well as in Singapore. Since then it has evolved into a family of sub-variants 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 makes it bind better to cells.
“The virus needs to bind tightly to cells to be more efficient at entering, and that might help the virus to be a bit more efficient at infecting people,” Pekosz said.
Yunlong Richard Cao, a scientist and assistant professor at Peking University, posted data on Twitter on Tuesday indicating that XBB.1.5 not only evades protective antibodies as effectively as the XBB.1 variant, which was highly immunologically evasive, but which is also better for binding to cells via a key receptor.
Columbia University scientists in a study published earlier this month in the journal Cellwarned that the rise of subvariants such as XBB could “further compromise the efficacy of current COVID-19 vaccines and result in a surge in infections and reinfections.”
XBB subvariants are also resistant to Evusheld, a cocktail of antibodies that many people with weak immune systems rely on to protect against covid infection because they do not mount a strong response to vaccines.
The scientists described the resistance of the XBB subvariants to antibodies from vaccination and infection as “alarming.” The XBB subvariants were even more effective at dodging the protection of omicron boosters than the BQ subvariants, which are also highly immune evasive, the scientists found.
Dr. David Ho, author of the Columbia study, agreed with the other scientists that XBB.1.5 probably has a growth advantage because it binds better to cells than its XBB relatives. Ho also said that XBB.1.5 is almost as immune to evasion as XBB and XBB.1, which until now were two of the most resistant subvariants to protective antibodies against infection and vaccination.
Dr. Anthony Fauci, who is stepping down as White House chief medical adviser, previously said that XBB subvariants reduce the protection that boosters provide against infection “by multiple times.”
“You might expect some protection, but not optimal protection,” Fauci told reporters during a White House briefing in November.
Fauci said he was encouraged by the case of Singapore, which had a large increase in XBB infections but did not see hospitalizations rise at the same rate. Pekosz said that XBB.1.5, in combination with vacation travel, could cause an increase in cases in the US. But he said the boosters appear to prevent serious illness.
“It appears that the vaccine, the bivalent boost provides continued protection against hospitalization with these variants,” Pekosz said. “It really emphasizes the need to get a boost particularly in vulnerable populations to provide continued protection against serious disease with these new variants.”
Health officials in the US have repeatedly called on the elderly in particular to make sure they are up to date with their vaccinations and receiving treatment with the antiviral Paxlovid if they have an advanced infection.
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