Yes they can! My
DS has has all his immunisations and recently also had whooping cough. It was awful. He was sick for about 6 weeks all up. I took him to the drs and they initally though he has asthma, then 2 days later I got a call from my doctor, saying "Please bring him back. I've been thinking about him and thought I should test him for whooping cough as there has been alot of reported cases in this area". Sure enough that's what he had. He was put onto medication which initally cleared it up, but then it came back.
The doctor said he would have a milder form of it but I would really hate to see a child that was serverly sick with it - it was horrible
.