The highly contagious omicron subvariant XBB.1.5 is responsible for the majority of new coronavirus infections in the U.S., according to data from the Centers for Disease Control and Prevention.
Agency estimates show that XBB.1.5 caused over 61% – or more than 3 in 5 – new coronavirus cases this week. That’s up from about 50% of infections last week.
While experts raised alarm over the strain, with the World Health Organization warning that it “may contribute to increases in case incidence globally,” coronavirus cases, hospitalizations and deaths in the U.S. are on the decline after worries over a potential surge due to holiday travel.
The CDC this week published what it characterized as the first estimate of the updated booster shot’s efficacy against symptomatic infection with XBB.1.5, finding that the shots are at least 40% effective against symptomatic illness from omicron subvariants XBB.1.5 and XBB among fully vaccinated adults within three months of the shot’s administration.
“Findings from this analysis of national pharmacy testing data show that a bivalent mRNA booster dose provided added protection against symptomatic XBB/XBB.1.5 infection for at least the first 3 months after vaccination in persons who had previously received 2, 3, or 4 monovalent vaccine doses,” the authors wrote. “All persons should stay up to date with recommended COVID-19 vaccines, including receiving a bivalent booster dose when eligible.”
While vaccines still appear to work against the new variant, Evusheld does not, prompting the Food and Drug Administration on Thursday to pull its emergency use authorization. Evusheld is an antibody treatment that was used as a pre-exposure treatment for people at high risk for severe COVID-19, like those with compromised immune systems.
The development was not a surprise considering the FDA earlier this month warned that it did not expect Evusheld to work on XBB.1.5.
In light of the FDA’s decision, the CDC on Friday advised that “people with a weakened immune system, their household members, and close contacts stay up to date on COVID-19 vaccines, develop a personal COVID-19 action plan, use masks and maintain distance, increase ventilation, test early if symptomatic, and start treatment if positive and eligible.”