Generally speaking, four-month-old babies can be vaccinated with polio vaccine, DPT vaccine and Haemophilus influenzae type B conjugate vaccine. 1. Polio vaccine: used for the prevention of poliomyelitis, also known as polio, the disease prevalence of the population is mainly concentrated in infants and young children between four months and five years old, usually two months of the baby began to inject the first injection of polio vaccine, three months injection of the second injection, four months injection of the third injection. 2. DPT vaccine: also called DPT triple vaccine, mainly to prevent diphtheria, pertussis and tetanus. Under normal circumstances, three-month-old babies can start to inject the DPT vaccine, and the second injection can be given at four months. 3. Haemophilus influenzae type B conjugate vaccine: mainly prevents invasive diseases caused by Haemophilus influenzae type B. There are three injections in total. Normally, babies at two months can take the first injection, the second injection at four months, and then the third injection at eighteen months. If you want to give your baby the vaccine, it is recommended to consult a professional doctor in detail and choose the vaccination according to the specific situation to avoid adverse reactions.