MODEL RELEASED. DPT vaccination. An 8-week-old baby receives its first triple vaccination against diphtheria, pertussis (whooping cough) and tetanus. The vaccine is delivered by a single subcutaneous injection. The DPT vaccine is given as a course of three injections at the ages of three, five and nine months, followed by a booster dose of diphtheria and tetanus vaccine at school entry age. An adverse reaction to the pertussis vaccine sometimes occurs, causing slight fever for several days. More serious reactions are very rare. Diphtheria, pertussis and tetanus can all be fatal in unimmunized children.