What's Going On With The New COVID FLiRT Variants?

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Fun name, not so fun epidemiology.

SARS-CoV-2 is making moves again - could a summer wave be coming?

Image credit: Roman Samborskyi/Shutterstock.com

Recently, we reported on the new family of COVID-19 variants that looked set to start overtaking the pack to become the most widespread. Now, surveillance data from both the US and UK show that the FLiRT variants, as they're called, seem to be living up to these predictions, as UK COVID cases tick up by 21 percent in just a week.

The FLiRT variants are named after the specific mutations they've picked up compared with earlier strains of the virus. In one location of the spike protein, an amino acid labeled "F" is switched for an "L", and in a second location an "R" is swapped for a "T". 

They're all offshoots of JN.1, itself part of the Omicron lineage, which became dominant on both sides of the Atlantic at the beginning of this year. Some early unpublished data posted to preprint server bioRxiv suggested that the extra mutations picked up by the FLiRT variants might make them more resistant to prior immunity from vaccines and infections, and better able to spread through the population.

According to data from the Centers for Disease Control and Prevention (CDC), one FLiRT variant called KP.2 was responsible for the greatest proportion of COVID-19 infections (28.2 percent) in the US in the two-week period ending on May 11. This means it has now overtaken JN.1, as suspected.

Granular data on which COVID-19 variants are dominating in the UK right now are not available, according to the UK Health Security Agency (UKHSA). However, the most recent surveillance data for the week ending April 30 showed a 21.2 percent increase in COVID cases, which the authority speculates is partly down to JN.1 subvariants, including KP.2.

Further afield, KP.2 was also recently detected in Australia and India.

So, should we be concerned?

According to Andy Pekosz, a professor of molecular microbiology and immunology at Johns Hopkins Bloomberg School of Public Health, an infection with JN.1 should still provide you with "pretty strong protection against all the FLiRT variants." So, if you've had COVID once already this year, you might still have a decent level of protection.

As for vaccines, Pekosz says the updated shots that were reformulated to target other variants in the Omicron lineage should produce some cross-reactive antibodies that may give some protection against KP.2. However, specific lab tests for this have not yet been done, and in any case, your immunity from vaccines is likely to be waning if it's been some time since your last shot. 

The CDC recommended that adults aged 65 and over receive a booster in February 2024, and continues to stress that regular booster vaccines are the best way to prevent serious illness and death from COVID-19.

In the UK, only certain groups of people are eligible to receive a vaccine under the country's National Health Service. At the time of writing, people aged 75 and over, children and adults with compromised immune systems, and care home residents are able to book a spring booster. Paying privately for a vaccine only recently became an option, but the popularity of this service has led to the recent news that the rollout is being expanded to more pharmacies. 

Masks are also making a comeback in some healthcare settings in the UK - but this time, COVID is not the reason. A surge in cases of the highly contagious bacterial infection pertussis, also known as whooping cough, has reportedly led some clinics to reinstate mask mandates for patients.

Will we see a summer wave of COVID?

"It's certainly possible," says Pekosz. But a wave driven by the FLiRT variants is very unlikely to send us back to the levels of infection and hospitalizations we were seeing in the early years of the pandemic.

Still, it's important that authorities continue to monitor what COVID is up to. The virus continues to pose a significant risk to vulnerable groups, and understanding when new variants are coming to the fore empowers us all to make choices that can help protect them.