FLirt Covid 19 Virus: Scientists are studying the FLiRT variants, subvariants of the Omicron lineage, which may be more contagious and evade immunity better. The FLiRT variants, derived from the JN.1 variant, are demonstrating increased 'fitness' and may become the dominant subvariants in Australia. Booster shots targeting Omicron XBB.1.5 provide significant protection against severe illness.