Will your last COVID vaccine work against new ‘FLiRT’ variants?

(NEXSTAR) — There are two new COVID-19 variants circulating, posing a threat to a summer surge.

The Centers for Disease Control and Prevention has been tracking the new variants, scientifically known as KP.2 and KP.1.1 since at least the start of 2024. They’ve been steadily growing in prominence ever since, and have garnered the nickname “FLiRT” because of their mutations.

The latest data shows KP.2 is the dominant strain in the U.S., comprising almost 25% of the tests that have been sequenced. KP.1.1 makes up about 8% as of the end of April. Both are sublineages of the JN.1 lineage of the Omicron variant, the main COVID variant for roughly three years.

Both FLiRT variants are considered very similar to JN.1, health officials say, with early data suggesting only a couple of changes in their spike proteins.

With the virus expected to spread as the summer months approach, it may be sparking concerns about whether the last vaccine dose you received is still protecting you. Ultimately, it depends on when you got your last dose.

In fall, an updated COVID vaccine was released. The CDC has recommended everyone 6 months old and older get the updated vaccines from Pfizer-BioNTech, Moderna, or Novavax. In February, a federal immunization committee voted in favor of recommending an additional dose for those ages 65 and up. Those between the ages of 6 months and 4 years old require multiple doses, the CDC says.

Previously, health officials have said the COVID vaccines would provide protection from the virus for “several months.” In a February update on the newest vaccine booster made available in September, the CDC said that while it had (from September to January) been effective, they expected that protection would “decline over time” as had been seen with previous doses. 

However, because the FLiRT variants are relatively new, there isn’t enough data to show whether the vaccine or immunity from a recent case of COVID will provide effective protection against them. 

Speaking with TODAY, Dr. William Schaffner, professor of infectious diseases at Vanderbilt University Medical Center, said lab studies so far have shown vaccines and immunity may only provide partial protection. Late last month, the World Health Organization recommended that future COVID vaccines formulations be based on the JN.1 variant, a close relative of the FLiRT off-shoots that reigned as the most common in the U.S. over the last few months.

As of Thursday, the CDC is reporting minimal COVID activity in wastewater nationwide, and virus-related hospitalizations and deaths, as well as the rate of patients visiting emergency departments testing positive for COVID, are down.

A spokesperson for the CDC tells Nexstar that the agency is “working to better understand [KP.2 and KP.1.1]’s potential impact on public health,” but notes that based on lab tests, there are “low levels of SARS-CoV-2 transmission overall at this time.”

“That means that while KP.2 is proportionally the most predominant variant, it is not causing an increase in infections as transmission of SARS-CoV-2 is low,” the spokesperson added. “Based on current data there are no indicators that KP.2 would cause more severe illness than other strains. CDC will continue to monitor community transmission of the virus and how vaccines perform against this strain.”

It’s too soon to say whether a new COVID vaccine will be created for the summer months. While the CDC recently eased guidance surrounding COVID, the agency still recommends everyone 6 months old and older get the updated COVID vaccine released in fall, if they haven’t already. Health experts are also continuing to encourage testing if you experience symptoms or are exposed, staying home if you’re sick, practicing good hygiene, and wearing a mask and social distancing when in public.