Phase II Clinical Trial of the Inactivated Rotavirus Vaccine

Inclusion Criteria: * Age Requirement: Infants and toddlers aged 2 to 71 months at the time of enrollment. * Provision of Legal Identification: Volunteers and their legal guardians or appointed representatives must provide valid legal identification documents. * Informed Consent: Legal guardians or appointed representatives of volunteers must have the capacity to understand the informed consent document and the research process, voluntarily participate, sign the informed consent form, and be able to comply with the requirements in the study as well as complete relevant visits on time. * No Previous Rotavirus Vaccination: Infants and toddlers enrolled in the study should not have received any rotavirus vaccines before enrollment. Exclusion Criteria: 1. First Dose Exclusion Criteria Subjects meeting any of the following exclusion criteria will be not eligible for enrollment: * Temperature Requirement: Axillary body temperature prior to vaccination is up to 37.3°C or more. * Allergic History: Subjects have a history of allergies to any component of the investigational vaccine (e.g., aluminum hydroxide), any history of vaccine allergies, suspected allergies, or any other severe adverse reactions. * Vaccine History: Subjects received any inactivated vaccines or subunit vaccines within 7 days (including the 7th day) prior to vaccination with the investigational vaccine, or any other live attenuated vaccines or COVID-19 vaccines within 14 days (including the 14th day) prior to vaccination. * Health Conditions: Subjects have known congenital abnormalities, developmental disorders, genetic defects, or severe malnutrition, among other conditions. * Immune-Related Diseases: Subjects have compromised primary or secondary immune function, human immunodeficiency virus (HIV) infection, lymphoma, leukemia, systemic lupus erythematosus (SLE), juvenile rheumatoid arthritis (JRA), inflammatory bowel disease, or other autoimmune diseases. * Gastrointestinal Conditions: Subjects have a history of intussusception or chronic gastrointestinal diseases. * Neurological and Mental Health: Subjects have a history of seizures, convulsions, cerebral palsy, epilepsy, mental illness, or a family history of such conditions. * Acute Illness: Subjects have experienced acute illnesses (e.g., fever) within 3 days prior to vaccination with the investigational vaccine. * Immune Therapy: Subjects have received immune-enhancing or immune-suppressing therapy within the last 3 months (continuous oral or intravenous administration for more than 14 days) prior to vaccination. * Coagulation Abnormalities: Subjects have a history of coagulation disorders (e.g., coagulation factor deficiency, coagulation disorders). * Organ Removal History: Subjects have a history of organ removal (e.g., thyroid, pancreas, liver, spleen) or have asplenia syndrome. * Participation in Other Clinical Studies: Subjects are currently or have plans to participate in other clinical studies before enrollment. * Special Conditions for Children Aged 24 Months and Below: For such children, additional exclusion criteria include difficult birth, resuscitation after suffocation, a history of neurological damage, premature birth (delivery before the 37th week of gestation), and low birth weight (less than 2500 grams). * Investigator's Discretion: The final exclusion criterion is the investigator's discretion to determine whether a subject is suitable for participation in the study. 2. Contraindication of the second and third doses of vaccine * Severe Adverse Reactions: Subjects experienced severe adverse reactions after receiving the previous vaccine dose. * No Longer Meeting Inclusion Criteria or Meeting First Dose Exclusion Criteria: New conditions that disqualify them from meeting inclusion criteria or that meet the exclusion criteria for the first dose occur after receiving the previous dose, as determined by the investigator. * Vaccination with Other Rotavirus Vaccines During the Study: Subjects received other rotavirus vaccines during the study period. * Other Exclusion Reasons as Determined by the Investigator: The investigator determines other reasons for exclusion.