Study of Live Attenuated Varicella Vaccine Co-administered with MMR Vaccine or DTaP Vaccine

Inclusion Criteria: * Infants aged 18-24 months; * have completed 3 doses of DTaP for primary immunization in their first year of life without the fourth dose of Dtap-containing vaccine; * have completed the first dose of MMR in their first year of life without a second dose of MMR; * Guardians of participants who are able to understand and voluntarily sign informed consent; * Provision of legal proof of identity. Exclusion Criteria: * Having a history of previous varicella vaccination; * Having a history of chickenpox, pertussis, diphtheria, tetanus, measles, mumps, and rubella; * Having a history of uncontrolled chronic or serious diseases, including but not limited to cardiovascular diseases, hematological diseases, liver and kidney diseases, digestive diseases, respiratory diseases, malignant tumors, major functional organ transplantation, etc.; * Presence of autoimmune diseases, immunodeficiency diseases (including but not limited to systemic lupus erythematosus, ankylosing spondylitis, autoimmune thyroid disease, asplenia, functional asplenia, HIV infection); * Presence of abnormal coagulation function (e.g. coagulation factor deficiency, platelet abnormality); * Having/Previous having a severe neurological disorder (epilepsy, seizures, or convulsions) or psychosis, or have a family history of psychosis; * Acute onset of various acute or chronic illnesses within the last 7 days, or known or suspected active infection; * Receipt of \> 14 days of immunosuppressive or o…