The purpose of this study is to evaluate the efficacy, immunogenicity and safety of S. Flexneriza-S. Sonnei Bivalent Conjugate Vaccine in infants and children aged from 6 months to 5 years.

Inclusion Criteria:

• Infants and children aged from 3 months to 5 years old;
• The legal representative voluntarily agrees to participate in the study and signed the informed consent form;
• The legal representative voluntarily agrees to comply with the requirements of the clinical study protocol, and they can participate in all planned follow-up;
• Subjects who didn't immuned with attenuated live vaccine within 14 days and inactivated vaccine within 7 days before vaccination;
• Axillary temperature ≤37.0℃;
• According to the medical history, physical examination and the judgment of the researcher, it is determined that the subject is in good physical condition.

Exclusion Criteria:

• Previous proven history of bacillary dysentery;

• Subjects who are allergic to tetanus toxoid, and have any history of other vaccination or drug allergy, or a fever above 39.5 ℃ after previous vaccination;

• Within 3 days before vaccination, suffering from acute diseases or in the acute episode of chronic disease or using antipyretic, analgesic and antiallergic drugs (such as acetaminophen, ibuprofen, etc.);

• Had severe bowel disease, and had symptoms such as diarrhea, abdominal pain, pus and blood stool and other symptoms in the past 3 days;

• With pathological jaundice confirmed by existing diagnosis;

• History of thrombocytopenia or other coagulation disorders with definite diagnosis;

• Known or suspected immunological deficiency (such as perianal abscess, which indicates that infants may have immune deficiency), and received long-term (≥14 days) immunosuppressive therapy (radiotherapy, chemotherapy, systemic glucocorticosteroids≥2 mg/kg/day, antimetabolic drugs and cytotoxic drugs) within half a year before vaccination, or confirmed that the parents were HIV infected;

• Received immunoglobulin / blood products treatment within 3 months before vaccination;

• Severe congenital malformations (functional impairment of important organs), severe malnutrition, developmental disorders and serious genetic diseases (such as severe thalassemia);

• Subjects with the following diseases:

  1. Serious liver and kidney diseases, cardiovascular diseases, malignant tumors and other chronic diseases;
  2. Diagnosis with infectious diseases such as tuberculosis, viral hepatitis and so on;
  3. Severe asthma;
  4. Systemic rash, dermatophyte, skin suppuration or blister;
  5. History or family history of convulsion, epilepsy, encephalopathy, mental illness;

• Planning to participate or currently participating in clinical trials of other vaccines or drugs;

• Any situation that the investigator believed may affect the study evaluation.