This study is an open, multicenter Phase IV clinical study to evaluate the safety of vaccination with Menhycia®. The study plan is to enroll approximately 3,000 infants at 3 months of age who have not been vaccinated with any epidemic encephalitis vaccine, and to administer a total of 3 doses of Menhycia®, with a minimum of 1 month between doses, and a booster dose of 1 dose of immunization is allowed at 12 months of age.

Inclusion Criteria:

• Infants 3 months of age who had not received any epidemic encephalitis vaccine at the time of screening
• The legal guardian or delegate has given informed consent, has voluntarily signed an informed consent form, and is able to comply with the requirements of the clinical study protocol

Exclusion Criteria:

First dose exclusion criteria

• Fever before vaccination, axillary temperature >37.0°C
• Congenital malformations or developmental disorders, genetic defects, severe malnutrition, etc.
• History of epilepsy, convulsions or seizures or history or family history of psychiatric disorders
• Acute infections or active chronic diseases, severe infectious or allergic skin diseases
• Known allergy to a component of the vaccine, especially to diphtheria toxoid, or to previous administration of the product
• Other circumstances that, in the judgment of the investigator, make participation in this clinical study inappropriate

Subsequent dose exclusion criteria

• Severe allergic reactions after a previous dose of vaccine
• Those with serious adverse reactions causally related to the previous dose of vaccination
• Other circumstances that, in the judgment of the investigator, make participation in this clinical study inappropriate