While generally it is thought that acquiring whooping cough, like some diseases, in early childhood usually in infancy gives a lifetime immunity - recent studies tend to show otherwise.In adults, it can recur but in milder form and without the typical "whooping sound" in infants. It is a highly communicable disease that affects the respiratory system, but highly preventable (up to 80% with DTaP vaccines and booster shots given at appropriate intervals. It is best to see (and report one suspected to have the disease) a doctor immediately if you suspect you have the disease.
Yes, though having whooping cough can give the body natural immunity, this is often temporary and therefore an adult or child can have it again. But when a person recieves complete vaccines with shots, the immune system acquires complete resistance against the condition. Here is a link for further reading: http://www.ask.com/wiki/Pertussis