Credit – Courtesy of Pfizer and Moderna

AAmid a continued surge, the U.S. Food and Drug Administration (FDA) has approved updated COVID-19 vaccines for the 2024-2025 respiratory infection season.

The new vaccines, made by Moderna and Pfizer-BioNTech, are largely the same as the original mRNA vaccines developed early in the pandemic, but they target KP.2, a different strain of the virus that has caused many of the rising case numbers this summer. The FDA initially recommended in early June that vaccine makers focus on the JN.1 lineage, which includes KP.2, but changing patterns of how variants cause disease led the agency to update its guidance in August, asking manufacturers to focus on KP.2.

Why are the new vaccines targeting this variant?

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 target KP.2 because the virus continues to mutate faster than manufacturers can keep up with a finely tuned vaccine — even with mRNA technology, which allows scientists to produce vaccines against a new target in just six to eight weeks. Testing that shot and scaling up production will take several more months.

The good news, though, 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 those variants developed. They all have different names because they each independently developed similar mutations. That means a vaccine that targets one variant will likely still be effective against others in the group, albeit at different 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 the previous XBB vaccine. A Pfizer spokesperson says testing showed similarly stronger immune responses with the updated KP.2 vaccine against JN.1 splices, including KP.3 and LB.1, compared to the XBB vaccine.

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The bad news is that the FLiRT mutations make it harder for antibodies that the body generates — either through exposure to the vaccine via 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 has allowed them to spread more quickly among people, though they don’t appear to cause more severe disease in most people.

Who should get the new jab?

The FDA approved both vaccines, from Moderna and Pfizer-BioNTech, for people 12 and older. For children ages 6 months to 11, the agency issued emergency authorization, allowing manufacturers to distribute the vaccine while additional safety and side effect data are collected in that age group. People over 65 remain at the highest risk of being hospitalized for complications related to COVID-19 — nearly 18 times as much as younger people, the CDC says.

When can I get vaccinated?

Both companies say they expect doses of their vaccines to be available at pharmacies and doctor’s offices in the coming weeks. Walgreens says the first appointments for COVID-19 vaccines will be Sept. 6. To help more doctors’ offices keep the vaccines in stock and encourage greater uptake, a Pfizer spokesperson says the vaccine will have a longer shelf life than previous vaccines and will come in smaller, pre-filled syringe packages of 10 to reduce waste.

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