What are the FLiRT Covid-19 variants and are they more contagious?

NEW YORK — Covid-19 sub-variants, nicknamed "FLiRT", have been the dominant forms of the virus circulating this year globally, according to the World Health Organisation.

The moniker FLiRT is an acronym for the locations of the mutations the variants share on the virus' spike protein.

One of them, called KP.2, has become the most commonly circulating variant in the US over the past month, according to the US Centres for Disease Control and Prevention.

Here is what you need to know about FLiRT.

How are the FLiRT variants different from previous variants?

The FLiRT variants, which also include KP.2's "parental" lineage JN.1, have three key mutations on their spike protein that could help them evade antibodies, according to Johns Hopkins University.

Are the FLiRT variants more contagious or likely to cause more severe illness?

Dr Aaron Glatt, chief of infectious diseases at Mount Sinai South Nassau Hospital in Oceanside, New York, and a spokesperson for the Infectious Diseases Society of America said he has not seen evidence of an uptick in disease or hospitalisations, based on the data he tracks and experience with his own patients.

"There have been some significant changes in the variants, but I think in recent times it's not been as important, probably because of the immunity many, many people already have" from prior illness and vaccination.

CDC data suggests that Covid-19-related hospitalisations have trended downwards in recent weeks and the number of patients in emergency departments who have tested positive for Covid-19 has been about flat for the past month.

Data suggests that Covid-19 rates are also down year-over-year.

The rate of Covid-19 hospitalisations is less than half than a year earlier, and the amount of the antiviral Paxlovid currently being prescribed for Covid-19 is down around 60 per cent from last year, according to analyst notes.

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Do current vaccines work against the FLiRT variants?

The current vaccines should still have some benefit against the new variants, Dr Glatt said.

Since 2022, health regulators have asked vaccine makers to design new versions of the Covid-19 vaccines to better target circulating variants.

Last month, Europe's regulator said vaccine makers should target the JN.1 variant.

US experts and regulators will meet to discuss vaccine design on June 5 after having postponed the meeting from May 16 in order to have more time to "obtain surveillance data and other information".

Makers of vaccines based on messenger RNA (mRNA) technology — Pfizer with partner BioNTech, and Moderna — say they are waiting for the June 5 meeting before settling on the design of their next vaccines.

Novavax, which makes a more traditional protein-based vaccine that takes longer to manufacture, has begun producing a shot targeting JN.1 consistent with recommendations from European regulators.

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