Vaccines!

Got my blood titers today showing what antibodies I have against varicella, measles, mumps, and rubella, proving my immunity. If this isn't proof that VACCINES WORK I don't know what is people. 
The reason it's still possible to get the flu after getting flu vaccine is because the flu is a rapidly changing virus that may be different than the antibodies you have from the vaccine. It's very difficult to predict what virus it will be. Which is why there's a new flu shot every year. 
Got. Vaccinated.