My daughter has had all her vaccines on schedule all her life - except for Pertussis (whooping cough).  Before she ever started school when she was 5 yrs old, the pediatrician said he was not giving it because of her medication.  He had to fill out a special form explaining it to the school system before she would be enrolled.  Now I am wondering, is it too late to get that vaccine?  She is 15 yrs old.  I remember reading recently that whooping cough is making a comeback.  How serious is this?