New COVID ‘FLiRT’ variants are spreading nationwide

CHICAGO — A new family of COVID-19 variants nicknamed “FLiRT” is spreading across the country, as vaccination rates in Chicago — as well as nationwide — remain concerningly low for some public health experts.

While symptoms and severity seem to be about the same as previous COVID strains, the new FLiRT variants appear to be more transmissible, said infectious disease expert Dr. Robert Murphy.

“A new, more contagious variant is out there,” said Murphy, executive director of Northwestern University’s Institute for Global Health and a professor of infectious diseases at the Feinberg School of Medicine. “COVID-19 is still with us, and compared to flu and RSV, COVID-19 can cause significant problems off-season.”

Murphy urged the public to get up to date on COVID shots, particularly individuals who are at higher risk for severe complications from the virus. While much of the population has some immunity from vaccination or previous COVID infections, Murphy noted that “with COVID-19, immunity wanes over time.”

One FLiRT variant, KP.2, is estimated to account for roughly a quarter of recent COVID cases, according to Centers for Disease Control and Prevention data from late April.

That means it has outpaced the previously most common strain, JN.1, which spurred much of the winter respiratory season's spike in COVID cases and hospitalizations nationwide, coinciding with a spate of flu and RSV infections around the same time.

The JN.1 variant is estimated to account for about 22% of recent COVID cases across the country, according to CDC data from late April.

Another FLiRT variant, KP.1.1, comprises over 7% of COVID cases nationwide, the CDC data shows. The name “FLiRT” is an acronym using the technical names for the mutations that caused the family of variants.

Hannah Barbian, a virologist at the Regional Innovative Public Health Laboratory at Rush University Medical Center, has been tracking various COVID variants in Chicago. She said her laboratory has detected the KP.2 variant in Chicago but not KP.1.1, though she believes that variant will likely be detected soon as well.

“In general, lineages that emerge in the U.S., we detect them in Chicago,” she said.

Barbian added that new COVID variants "aren't unexpected."

“In this case, they’re only slightly different from variants that were most prevalent before,” she said.

But some public health experts expressed concern that the new variants have emerged amid low uptake of the updated COVID vaccine locally as well as across the country.

“It is concerning that vaccination rates are so low. Because the best way to be protected is vaccination,” said Dr. Stephanie Black, interim deputy commissioner of the disease control bureau for the Chicago Department of Public Health. “It’s helpful to have the most updated vaccine.”

She added that a new updated COVID vaccine will likely to be available in the fall.

Sixteen percent of Chicago residents are up to date on COVID vaccination, according to the Department of Public Health statistics, which are based on Illinois Comprehensive Automated Immunization Registry Exchange data.

The numbers are higher for older residents, with 34% of those aged 65 to 74 and almost 39% of those 75 and up having received an up-to-date booster shot.

City officials, though, say the number of residents vaccinated might be higher based on National Immunization Survey data.

Nationwide, about 23% of adults and 14% of children were reported to be up to date on COVID vaccines as of late April, according to the CDC, based on data from the National Immunization Survey.

“For people who have fragile immune systems, they should take precautions around large crowds and places where they can be exposed,” said Dr. Elizabeth McNally, director of the Northwestern University Feinberg School of Medicine Center for Genetic Medicine. “For older people, it’s generally a good idea to stay up to date on vaccinations since immunity does wane with age.”

In February, the CDC recommended that Americans 65 and up get another dose of the updated vaccine that became available in September, if at least four months had passed since their most recent shot.

McNally said it’s hard to know the impact of new variants since “there is not a great deal of testing going on these days.”

But she noted that there doesn’t appear to be an increase in COVID hospitalizations, nor has she seen uptick in infections in her patients, who “tend to be quite sick at baseline and contact me when they are exposed or sick.”

COVID hospitalizations and deaths are on the decline in Chicago and nationwide, according to the city health department and CDC. The Chicago region's current COVID-19 hospital admission level is low, as is most of the United States, according to the CDC.

While vaccination rates have tapered off, McNally noted that this “is on the backdrop of a great deal more immunity from repeated exposures from natural infection and vaccination,” compared with the early stages of the COVID pandemic.

“This translates to quicker recoveries and less prolonged illness when people do get COVID,” she said. “In 2020, we were dealing a virus for which humanity had little immunity. That is, thankfully, very different now.”