DTaP immunization: DTaP vaccine protects from diphtheria, tetanus (lockjaw), and pertussis (whooping cough). It is designed to be given in a series of 5 doses. DTaP was first licensed in 1991, and research shows that it is much safer than the previous formulation, DTP. Currently, there are three licensed formulations of the DTaP vaccine. Many different clinical trials were conducted on each vaccine to make sure of its safety. Results from clinical trials showed that these vaccines are very safe for infants and children.