DTP and DTaP vaccines are a shot of medicine that help protect your child from the diseases diphtheria (dip-theer-e-uh), tetanus (tet-nuss), and pertussis (per-tuh-sis). These 3 diseases were very common before vaccines were found and caused many deaths every year. Most children who get all their shots will be protected during childhood. The risk of getting these diseases will go back up again if children are not immunized.