DPT (DTP) vaccination is one of the recommended childhood immunizations and should begin during infancy. In most parts of the United States, DPT immunization is required before starting school. A minimum of 3 injections should be given, and 5 injections is strongly recommended. DPT (DTP) immunization is usually a series of injections given to children at ages 2 months, 4 months, 6 months, and 15 to 18 months. A booster is given before starting school (age 4 to 6).