Flu vaccine is far and away the most underutilized.
The flu can definitely set you up for bacterial pneumonias.
Physicians who care for adults generally don't think about vaccines as much as pediatricians do, and adults think of vaccines as a kid thing.
Pertussis is a disease that adolescents and adults give to children.
I've never seen this level of anger at parents who've chosen not to vaccinate their children.
If you've had a cough that lasted weeks, a cough that just doesn't seem to go away, chances are it was pertussis.