There are Class I and Class II vaccines for children. Class I vaccines are mandatory by the state and are given to children free of charge by the state. Class I vaccines include hepatitis B vaccine, BCG vaccine, polio vaccine, diphtheria vaccine, and measles vaccine. Class II vaccines include varicella, hand, foot and mouth disease, rotavirus, streptococcus pneumoniae, as well as influenza and encephalitis B vaccines. Class II vaccines are usually given at parents’ own expense, and they are also mandatory vaccines that can effectively prevent various infectious diseases.