The Tdap Vaccine is a class of combination vaccines against three infectious diseases in humans: diphtheria, pertussis, and tetanus.

Diphtheria: Your doctor may be able to diagnose diphtheria just by looking at your throat and spotting the gray mucus on your tonsils and throat. In addition, your doctor may do a throat culture. 

Pertussis: Sometimes your doctor can diagnose pertussis just by listening to your cough. Your doctor also may want to do a throat culture (use a swap to get a mucus from your throat to test), a blood test or even a chest X-ray. 

Tetanus: Your doctor can diagnose tetanus by doing a physical exam and looking for symptoms like muscle spasms, stiffness and pain.