The Group ac flu vaccine is mainly used to prevent influenza disease. There are generally two types of vaccines: one is polysaccharide; the other is conjugate. The polysaccharide vaccine is generally free of charge and requires two doses for children aged 6-18 months, which is a mandatory vaccine for every baby. Each baby’s vaccination book has the corresponding time and what vaccines are needed, so just follow the ones in the book. Before giving the vaccine to your baby, observe whether your baby has a cold or a fever. Another type of conjugate vaccine is required at your own expense, and the two are basically similar in function.