This vaccine is used to help prevent diphtheria, tetanus (lockjaw), and pertussis (whooping cough) in children and adults who have been vaccinated for these diseases in the past. It may also be used during the third trimester of pregnancy to help prevent pertussis in the newborn baby. Vaccination is the best way to protect against these life-threatening diseases. This vaccine works by increasing the body's natural defense (immunity) against the bacteria. Booster doses of this vaccine are needed since immunity can decrease over time.

Vaccines may not fully protect everyone who receives them.