Three-month-old babies usually need to be vaccinated with polio vaccine and DPT vaccine, among others. 1. Polio vaccine: Children are vaccinated once in February, March, April and at the age of 4 years. It is used to prevent acute infectious diseases caused by poliovirus. Poliovirus mainly damages the motor neurons in the anterior horn of the spinal cord and may cause hemiplegia, paralysis of the respiratory muscles and death in children. Polio vaccination can greatly prevent children from contracting poliovirus. 2. DPT vaccine: 3 times at 3~12 months of age, each time at an interval of 4~6 weeks. Pertussis vaccine can prevent whooping cough, diphtheria and tetanus, three diseases that are very harmful to children. Adverse reactions such as fever, nausea, vomiting, redness and swelling at the vaccination site are likely to occur after vaccination. If your baby has a major adverse reaction after vaccination, parents should take your child to the hospital promptly and respond to the doctor’s medical history to prevent a dangerous situation for your child.