The research objective is to evaluate the safety and tolerability of the recombinant Group B meningococcal vaccine (E. coli) and explore its preliminary immunogenicity.

This is a Phase I, single center, randomized, double-blind, placebo-controlled clinical trial conducted in Guangxi Province, China. The purpose of this study is to evaluate the safety and tolerability of the recombinant Group B meningococcal vaccine (E. coli) and explore its preliminary immunogenicity. Expected to include 300 subjects, divide them into 5 age groups of 18-50 years old, 6-17 years old, 2-5 years old, 6-23 months old, and 3-5 months old, and 2 dose groups, a total of 10 groups, with 30 people in each group. The experimental group and placebo control group are 20 people and 10 people, respectively.

Inclusion Criteria:

• Age range from 3 months to 50 years old, legal guardian and/or individual can provide legal identification;
• The subjects and/or their legal guardians have the ability to understand the research procedures, agree to participate in the study (and/or their legal guardians agree to the child's participation in the study), and sign an informed consent form;
• The subjects and/or their legal guardians are able to participate in all planned follow-up visits;
• On the day of enrollment, the axillary temperature was less than 37.3 ℃;
• Standards for certain groups of people:
• Subjects ≥ 2 years old: laboratory test indicators (as specified in the protocol) within the normal range, or those with abnormalities but no clinical significance (evaluated by clinical doctors);
• Female participants of childbearing age: Agree to take effective contraceptive measures within 6 months from enrollment to full vaccination.

Exclusion Criteria:

• Have received any Group B meningococcal vaccine in the past;
• A history of invasive diseases caused by meningococcus or gonococci;
• Pregnant or lactating women;
• Have any history of severe allergies to vaccines or drugs in the past, such as allergic shock, allergic laryngeal edema, allergic purpura, thrombocytopenic purpura;
• Suffering from serious heart disease, liver disease, kidney disease, congenital malformations, developmental disorders, and genetic defects (including but not limited to Down syndrome, moderate to severe thalassemia, etc.) that may interfere with the progress or completion of the study;
• Diagnosed as having congenital or acquired immunodeficiency, or suspected of having serious chronic or systemic diseases that may interfere with the conduct or completion of the study, such as active tuberculosis, hepatitis B, hepatitis C, human immunodeficiency virus (HIV), syphilis infection, etc;
• Individuals with encephalopathy, uncontrolled epilepsy, seizures, and other progressive neurological disorders, or a history or family history of mental illness;
• Suffering from contraindications for intramuscular injection such as thrombocytopenia, any coagulation disorders, or receiving anticoagulant therapy;
• Received immunosuppressive therapy within 3 months prior to vaccination, such as continuous use of systemic glucocorticoid therapy for more than 2 weeks, such as prednisone or similar drugs>5mg/day (note: local and inhaled/nebulized steroids can be used);
• Asplenia or splenectomy, functional asplenia caused by any circumstances;
• Subjects with hypertension (systolic blood pressure ≥ 140mmHg and/or diastolic blood pressure ≥ 90mmHg, suitable for adults);
• Suffering from acute illness or in the acute phase of chronic illness, or using antipyretic, analgesic, and antiallergic drugs (such as acetaminophen, ibuprofen, aspirin, etc.) three days before the first dose of vaccination;
• Within 7 days (≤ 7 days) prior to enrollment, received inactivated vaccines, and within 14 days (≤ 14 days) received live attenuated vaccines;
• Has received blood or blood related products or immunoglobulin (hepatitis B immunoglobulin is acceptable) within 3 months prior to enrollment;
• Premature infants (gestational age<37 weeks), low birth weight infants (birth weight<2500g), and infants with a history of abnormal labor (only applicable to the 3-5 month and 6-23 month age groups);
• Plan to move before the end of the study or leave the local area for a long time during the scheduled study visit;
• Participating in or planning to participate in clinical trials of other drugs in the near future;
• The researchers believe that there are any conditions in the subjects that may interfere with the evaluation of the research objectives.