People dont 'get immunity' to seasonal viruses, thats why theres constantly updated flu shot every year. Not enough people get the shot, kncluding me sometimes, but with the flu its mostly just a mild irritation for a few days with minimal lasting effects. Still, less people would get it if everyone would mask up and get vaccinated, as we saw during covid when barely anyone got the flu due to wearing masks. This isnt a complicated social problem, masks protect people from germs of all kinds, and the more people wearing them, especially when theyre feeling sick, the better off the rest of the population will be. Especially since covid can have such lasting effects.