I think the key difference might be that flu mutates quickly, so each year we actually get a flu vaccine for a variety of the most likely strains. While for Cov

I think the key difference might be that flu mutates quickly, so each year we actually get a flu vaccine for a variety of the most likely strains. While for Covid after 2 years of mutations, the doses of the initial vaccine are still very effective against severe disease. At the very least the current trend of mass vaccinating people with boosters every 3-6 months seems completely unsustainable (and possibly harmful), except for possibly those in the highest risk categories.