Flu shots are not mandatory, and not all country have mandatory vaccination schemes, relying on the health system's ability to convince people. Also, antivaxxer

Flu shots are not mandatory, and not all country have mandatory vaccination schemes, relying on the health system's ability to convince people. Also, antivaxxers usually try to avoid the mandatory ones, are often quite immune to Occam's Razor, and apply critical thinking only to their opponent's arguments :)