The difference between Meningococcal A and Conjugate Meningococcal A+C is that Meningococcal A is a polysaccharide vaccine covering only Meningococcal group A, which is a free vaccine, while Conjugate Meningococcal A+C is a conjugate vaccine covering Meningococcal groups A and C, which is a self-funded vaccine. Group A polysaccharide vaccine belongs to Class I vaccine, i.e. free vaccine in China, the bacterial group only covers group A of encephalitis, and the vaccine technology belongs to polysaccharide vaccine, and the antibody produced by the polysaccharide vaccine is related to the age, and it is very weakly immunogenic to children <2 years old, and there is no immune memory, so the protection strength and effect are limited. AC-conjugate vaccine is a self-funded vaccine, the flora covers group A and group C of influenza, and the vaccine process is conjugate vaccine, which has immune memory after inoculation, so AC-conjugate vaccine has a better protective effect on children under 2 years of age, and the protection is more extensive. Therefore, the advantage of group A polysaccharide vaccine is that it is free of charge, but the protection is limited, while AC-conjugate vaccine for encephalitis is more comprehensive and safer for infants and young children, but the disadvantage is that the vaccine needs to be self-funded.