MODEL RELEASED. Four year old child receiving a pre-school immunisation against diphtheria, pertussis (whooping cough) and tetanus, also known as DPT vaccination. DPT immunisation is usually given in three courses when the child is three, five and nine months old. Booster doses are then given at nursery or primary school ages. The vaccine does not provide complete immunity to diphtheria and pertussis but it does reduce the risk of serious illness with these infections. Protection against tetanus is not permanent and needs to be boosted every ten years or at the time of any dirty skin laceration, if vaccination has not been performed in the last five years.