As of the end of March, the KP.2 variant accounted for about 4% of infections in the U.S., according to the CDC, while its parent strain, JN.1, was responsible for over 50% of infections at that time. By early May, KP.2 had surged to make up about 28% of infections, surpassing JN.1 as the dominant variant.
KP.2 is one of several variants referred to as “FLiRT variants,” named after the specific mutations they possess. The emergence of these variants is particularly significant as experts determine the composition of the fall COVID vaccine.
The mutations termed “FLiRT” or “FLip” occur at specific positions in the spike protein – positions 456, 346, and 572. Viruses like SARS-CoV-2 mutate frequently, and when they mutate to evade antibody recognition, it often weakens their ability to bind to cells. Subsequent mutations may then improve binding. The fact that different variants are acquiring the same mutations suggests that this combination of mutations enhances the virus’s ability to achieve these goals efficiently.
Understanding FLiRT variants
“FLiRT variants” is a term used to describe a family of variants, including KP.2, JN.1.7, and others starting with KP or JN, that have independently acquired the same set of mutations, a process known as convergent evolution. These variants are all descendants of the JN.1 variant, which has been predominant in the U.S. for several months.
Getting an idea of official figures in Australia is difficult because fewer people now test and register their cases. If we look at the NNDSS, there were 20,699 cases reported across the country between April 1 and April 30.
This is compared to 25,423 cases that have currently been reported up to May 23.
That’s an increase of 4,724 on April’s figures.
Paul Griffin, an infectious disease physician and clinical microbiologist at the University of Queensland, says it’s because the virus continues to evolve.
“What we have seen many times before and also at the moment is when the virus changes significantly, as is the case with the FLiRT mutation, protection from past infection and vaccination doesn’t work so well,” Dr Griffin told ABC news.
Infections & vaccinations
A recent JN.1 infection should provide strong protection against all FLiRT variants, as the differences are minimal, involving only one or two amino acid changes. Variants older than JN.1 are less likely to offer substantial protection.
Vaccines designed around the XBB.1.5 variant generate some cross-reactive antibodies against JN.1. However, newer FLiRT variants may be slightly less responsive. With waning immunity over time, particularly several months after vaccination, additional doses may be recommended, especially for high-risk groups.
It’s also the time of year when bodies like the WHO and FDA recommend formulations for the next COVID vaccine. The WHO has advised using the JN.1 lineage for upcoming vaccines. The FDA has postponed its meeting to finalise the fall 2024 vaccine formula to early June, allowing more time to monitor which FLiRT variant will become dominant.
What you need to know about FLiRT variants
The symptoms of FLiRT variants are similar to previous variants, with most cases being mild due to stronger immunity from past vaccinations and infections. The infectious period remains the same, with individuals contagious one to two days before symptoms appear and a few days after symptoms subside.
Antivirals like Paxlovid remain effective against FLiRT variants, including KP.2 and JN.1. Other antiviral drugs like molnupiravir and remdesivir are also expected to work against these variants. Pharmaceutical companies continuously test these drugs against new variants to ensure their efficacy.
If you are due for a COVID-19 booster, staying up do date will help maintain your protection against severe illness and hospitalisation.
They are especially important for anyone aged 65 years or older and people at higher risk of severe COVID-19.
At Heathershaw’s Vaccination Clinic, appointments are available for the latest COVID-19 vaccinations. Bookings can be made online here.
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