Immunization from measles protects you from measles, and when enough people vaccinate, society at large is better protected.
Not so with the flu. Flu comes back year after year and never goes away, even if everyone gets vaccinated, and the vaccinated can still catch the flu. That is why it is legitimate to ask the Left how long the mask mandates and travel restrictions, etc. will continue. If it is until covid is beaten, then they don't have a plan for stopping any of the societal restrictions, and they will have to be voted out of office to bring things back to normal.