Tdap Vaccine, Adacel Vaccine Active Booster Immunization for Tetanus, Diphtheria & Pertussis **Refrigerated (RX)Tdap Vaccine Overview and Schedule Adacel is a vaccine used as a booster to protect against tetanus, diphtheria, and pertussis (whooping cough). It is approved for adolescents and adults aged 10 to 64 years. For younger children, a different vaccine called DTaP is recommended. Diseases prevented: Tetanus (T): A serious bacterial infection characterized by painful muscle stiffness and spasms, often referred to as "lockjaw." Diphtheria (d): A bacterial