Chances are, at least one person you know—and probably many people you know—have caught COVID-19 this summer. Ever since the “FLiRT” variants emerged this spring, the U.S. has been hit with one new variant after another, leading to a seemingly never-ending wave of cases. The amount of virus in wastewater has steadily risen since May and levels are now “very high,” in part because there’s yet another new variant on the scene: KP.3.1.1.
[time-brightcove not-tgx=”true”]KP.3.1.1 was to blame for more than a third of new COVID-19 cases in the U.S. during the two weeks ending Aug. 17, U.S. Centers for Disease Control and Prevention (CDC) data show. And that’s a lot of cases: about one in 34 people in the U.S. currently has COVID-19, independent data scientist and infectious-disease modeler Jay Weiland tells TIME. CDC data also show that lots of people are testing positive and that hospital visits and deaths related to COVID-19 are on the rise.
What will KP.3.1.1 do next? Here’s what to know.
Like other variants that have recently become widespread in the U.S., including KP.2 and KP.3, KP.3.1.1 descended from JN.1, the Omicron relative that caused this past winter’s surge. Weiland considers KP.3.1.1 a “sibling” of the original FLiRT strains, because they have the same “parent” variant but are slightly different in composition.
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KP.3.1.1 has some changes that have allowed it to take off, according to pre-publication research posted online in July. It seems to be more infectious than KP.3 and better at evading antibodies generated both by previous infections and the COVID-19 vaccines distributed this past fall, the study says. A medication authorized by the U.S. Food and Drug Administration (FDA) to prevent COVID-19 illnesses among immunocompromised people also does not seem to work as well against KP.3.1.1 compared to prior variants, according to another pre-publication study posted online in August.
The silver lining of our COVID-filled summer is that many people have fresh immunity from recent cases. That means KP.3.1.1 doesn’t have as many vulnerable people to infect as it would have if it had become dominant a couple months ago, Weiland says.
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“I think we’re at the peak of this summer wave,” he says. KP.3.1.1’s ascent might prolong the surge a bit, but Weiland thinks it’s unlikely to lead to a major second spike given how much immunity there currently is in the population.
The exception may be among kids who are returning to school while COVID-19 is still spreading widely. There may be a noticeable uptick in cases within that age group, Weiland says.
On Aug. 22, the FDA greenlit a new COVID-19 vaccine for the 2024-2025 respiratory disease season, and it was designed to target KP.2. Since KP.2 is a close relative of KP.3.1.1, the new shot is likely to work fairly well against the currently circulating variant. These updated shots should be available to people of all ages in the coming weeks, according to the manufacturers, Pfizer-BioNTech and Moderna—good timing, with lots of virus still going around.
Novavax is also seeking regulatory approval of a shot meant to target JN.1, which would likely also provide some protection against its descendant KP.3.1.1.
