Introduction to FLiRT Variants
The FLiRT variants of the SARS-CoV-2 virus, responsible for COVID-19, have dominated global circulation this year, as reported by the World Health Organization. FLiRT stands for the locations of mutations these variants share on the virus’ spike protein. Notably, the KP.2 variant has recently become the most prevalent in the United States, according to the Centers for Disease Control and Prevention (CDC).
Mutations and evasion of antibodies
The FLiRT variants, including KP.2 and its “parent” lineage, JN.1, have three significant mutations on their spike protein. These mutations potentially enhance their ability to evade antibodies, as noted by Johns Hopkins University.
Contagiousness and severity of illness
Dr. Aaron Glatt, chief of infectious diseases at Mount Sinai South Nassau Hospital in New York, and spokesperson for the Infectious Diseases Society of America, has observed no significant increase in disease severity or hospitalizations related to these variants. He attributes this to widespread immunity from prior infections and vaccinations.
CDC data corroborates this, showing a downward trend in COVID-related hospitalizations and stable emergency department cases over the past month. Year-over-year, COVID rates have declined, with hospitalization rates less than half of what they were a year ago and prescriptions for the antiviral Paxlovid down by 60%.
Vaccine efficacy against FLiRT variants
Current vaccines’ effectiveness
Dr. Glatt believes that existing vaccines still offer some protection against the new variants. Since 2022, health regulators have directed vaccine manufacturers to adapt their formulas to better target emerging variants. Last month, European regulators recommended targeting the JN.1 variant for new vaccine designs.
Upcoming vaccine developments
U.S. experts and regulators are scheduled to meet on June 5 to discuss vaccine design, a meeting postponed from May 16 to gather more data. Pfizer and BioNTech, along with Moderna, are awaiting the outcomes of this meeting to finalize their next vaccine designs. Meanwhile, Novavax has already begun producing a vaccine targeting JN.1, in line with European guidelines.
The FLiRT variants, while containing notable mutations, have not shown evidence of increased severity or transmissibility, likely due to existing immunity levels. Current vaccines are expected to retain some effectiveness, with new formulations in development to better address these variants.
