you need a flu shot every year/season because (HA-

Last updated: 8/7/2022

you need a flu shot every year/season because (HA- haemoagglutinin; NA-neuroaminidase): flu virus gets rid of its HA and NA and replace them with completely new ones every year the virus can change its HA and NA every year, so a new shot is needed to teach your immune system how to recognize the changed HA and NA your immune system weakens after a year-so you have to get another shot to get the system strong enough to attack the virus antigen shift occurs every year