Amid an ongoing surge, the U.S. Food and Drug Administration (FDA) has approved updated COVID-19 vaccines for the 2024-2025 respiratory disease season.
The new shots, made by Moderna and Pfizer-BioNTech, are largely the same as the original mRNA vaccines developed at the start of the pandemic—but they target KP.2, a different strain of the virus that has been causing many of the rising number of cases this summer. The FDA initially recommended in early June that vaccine makers target the JN.1 lineage—of which KP.2 is a part—but changing patterns in which variants are causing disease led the agency to update its advice in August, asking manufacturers to focus on KP.2.
[time-brightcove not-tgx=”true”]KP.3 variants currently account for nearly half of COVID-19 infections in the U.S., and KP.2 variants cause about 14.4% of cases, according to the U.S. Centers for Disease Control and Prevention. The new vaccines are targeting KP.2 because the virus continues to mutate more quickly than manufacturers can follow them with a perfectly matched vaccine—and that’s even with the mRNA technology, which allows scientists to produce vaccines against a new target in just six to eight weeks. Testing that shot, and scaling up manufacturing, takes a few more months.
The good news, however, is that all of the JN and KP variants are related and belong to a group known as FLiRT, an acronym that encompasses the mutations these variants developed. They all have different names because they each developed similar mutations independently. That means that a vaccine targeting one will likely still be effective against others in the group, although at varying levels. A Moderna spokesperson says its updated KP.2 vaccine generated stronger immune responses against JN.1 variants, including KP.2 and KP.3, compared to its previous XBB vaccine. A Pfizer spokesperson says its tests showed similarly stronger immune responses with its updated KP.2 vaccine against JN.1 offshoots, including KP.3 and LB.1, compared to its XBB shot.
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The bad news is that the FLiRT mutations make it difficult for antibodies that the body generates—either from exposure to the vaccine through an infection or a vaccine—to neutralize the virus. But these changes also make it harder for the virus to attach to and infect cells. But overall, the ability of FLiRT variants to evade antibody defenses have allowed them to spread more quickly among people, although they don’t seem to cause more serious disease in most people.
The FDA approved both vaccines from Moderna and Pfizer-BioNTech for people 12 years and older. For children ages six months to 11 years, the agency issued an emergency use authorization, which allows manufacturers to distribute the vaccine while additional data on safety and side effects in that age group continue to be collected. People over age 65 continue to be at the highest risk of being hospitalized for complications related to COVID-19—nearly 18 times the rate of younger people, according to the CDC.
Both companies say they expect doses of their vaccines to be available at pharmacies and doctors’ offices in the coming weeks. Walgreens says its first appointments for COVID-19 vaccines will be on September 6. In order to help more doctor’s offices stock the vaccines and encourage greater uptake, a Pfizer spokesperson says its vaccine will have a longer shelf life than its past vaccines and come in smaller, pre-filled syringe packs of 10 to reduce waste.
