The fourth dose of DPT vaccine is usually administered at 18~24 months of age after the pediatric primary immunization. DPT vaccine is a vaccine against pertussis, diphtheria, tetanus and other diseases, including adsorbed DPT vaccine and adsorbed acellular DPT vaccine, its basic immunization is 3 shots, which can be given from the age of 3 months to the age of 12 months, with an interval of 4-6 weeks between each shot, and the fourth booster is usually given at the age of 18~24 months after the basic immunization. It should be noted that people suffering from encephalopathy, uncontrolled epilepsy and other progressive neurological diseases, and people suffering from acute diseases, severe chronic diseases or in the acute exacerbation of chronic diseases and fever should be prohibited from receiving adsorbed DPT vaccine; and people suffering from acute infectious diseases, including those in the recovery period and those with fever should be deferred from receiving adsorbed acellular DPT vaccine. In addition, after some children receive this kind of vaccine, adverse reactions such as redness, swelling, pain and itching may appear locally at the injection site, or systemic adverse reactions such as low fever, irritability, crying, anorexia, vomiting and mental depression, etc., which can be relieved on their own without treatment. However, if moderate fever occurs, symptomatic treatment should be timely, and if there are other serious adverse reactions should also seek medical attention.