For three-month-old babies, the following preventive vaccinations are required: first, the diphtheria vaccine. The diphtheria vaccine prevents three main diseases, namely whooping cough, diphtheria, and tetanus. After children are vaccinated with diphtheria, the probability of these three infectious diseases will be significantly reduced. Secondly, children need to be vaccinated against polio, which is mainly to prevent polio. Polio can cause hemiplegia and delayed development of one side of the lower leg in children with polio. Therefore, when children reach three months of age, they should be vaccinated with polio vaccine and polio vaccine in a timely manner.