Closeup of clinician's hands getting vaccine dose ready
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Vaccine advisers to the Food and Drug Administration on Thursday voted unanimously to recommend updating the COVID-19 bivalent booster vaccines to tackle the highly prevalent XBB omicron subvariant of SARS-CoV-2 in time for fall distribution. As recommended, the new shots would be monovalent, targeting a single strain of the virus.

The news arrived as the Centers for Disease Control and Prevention released data showing that the current booster vaccine’s efficacy against omicron has dropped about 6% in seniors. This shift is due in some measure of immune evasion during the Omicron XBB.1.5 subvariant period when compared to the BA.5 period, it noted. 

The currently available bivalent COVID-19 booster vaccines include a formulation that targets BA.4 and BA.5 omicron subvariants and the original SARS-CoV-2 virus. XBB and other omicron subvariants began cropping up in the fall of 2022, when the bivalent shots were rolled out. Although not widespread in the United States at the time, these new subvariants have since become ubiquitous and have been able to skirt vaccine-derived immunity. 

Overall, however, since being introduced, the bivalent shots have been significantly protective against COVID-19 infection in seniors. And the latest data show continued protection against death from the disease with no significant waning of efficacy for up to six months in this age group, the agency noted.

Makers of all U.S.-approved COVID-19 vaccines, including Pfizer/BioNTech, Moderna and Novavax, have been working on new vaccine formulations, and will follow the FDA’s lead in which variant to target for their fall shots. The FDA advisers favored development of shots that protect against the XBB.1.5 subvariant, Reuters has reported

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