New vaccine aims to tackle two viruses behind hand, foot, and mouth disease

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Healthy participants aged 18-59 years, 6-12 years, and 6-71 months. * Participants and/or their guardians can understand and voluntarily sign the informed consent form (participants aged 8-12 years require dual signatures from both participants and their guardians). * Willing and able to comply with all visit schedules, sample collection, vaccine administration, and other trial procedures. * Provide legal identification of the participants and/or their guardians. Exclusion Criteria: * History of hand, foot, and mouth disease or EV71 vaccination. * Known severe allergy to the vaccine or vaccine components, such as urticaria, respiratory distress, and angioedema. * Congenital abnormalities or developmental disorders, genetic defects (such as Down syndrome, thalassemia, or G6PD deficiency), severe malnutrition, etc. * Based on medical history and physical examination, the presence of severe chronic diseases, severe cardiovascular diseases, uncontrolled hypertension or diabetes, liver or kidney diseases, etc. * Based on medical history and physical examination, the presence of autoimmune diseases, immunodeficiency diseases, and/or blood diseases (including but not limited to systemic lupus erythematosus, ankylosing spondylitis, thyroidectomy, autoimmune thyroid disease, any form of malignancy, asplenia, functional asplenia). * Based on medical history and physical examination, abnormal coagulation function (such as coagulation factor deficiency, coagulation disorders, platelet abnormalities) or obvious bruising or bleeding disorders. * Based on medical history and physical examination, the presence of severe neurological diseases (epilepsy, convulsions, or seizures), mental illness, or corresponding family history. * Long-term use (more than 14 days) of corticosteroids or other immunosuppressive agents (excluding corticosteroid sprays for allergic rhinitis and surface corticosteroid treatment for acute non-complicated dermatitis) or cytotoxic therapy or planning to receive such treatment during the trial. * History of long-term alcohol abuse or drug abuse. * Females who are breastfeeding, pregnant, or planning to become pregnant within 90 days, or females with positive pregnancy test results. Note: male participants whose spouse plans to become pregnant within 90 days are also included. * Received immunoglobulin and/or other blood products in the past 3 months or planning to receive such treatment during the trial. * Received other investigational drugs or vaccines within the past 30 days or planning to receive such drugs or vaccines during the trial. * Vaccinated with attenuated live vaccines within the past 14 days or subunit or inactivated vaccines within the past 7 days. * Suspected or confirmed fever within 72 hours before vaccination or axillary temperature \>37.0℃ on the day of vaccination. * Clinical laboratory testing shows laboratory abnormalities beyond the reference range and with clinical significance (applicable only to Phase I clinical trials for adults/6-12-year-old children/24-71-month-old children): A. Complete blood count: white blood cell count, hemoglobin, platelet count.B. Blood biochemistry: alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TBIL), creatinine (CR), fasting blood glucose (Glu).C. Urine routine: urine protein (PRO). * Any acute illness (with or without fever) or exacerbation of chronic illness within the past 7 days. * According to the investigator's judgment, there are any other factors that make the participant unsuitable for participation in the clinical trial.