Subjects will be recruited and divided into 3 groups:

1. Experimental Group (408 subjects): combined immunization of PPV23 and IIV4;
2. Control Group A (408 subjects): IIV4 only;
3. Control Group B (408 subjects): PPV23 only;

All blood samples will be collected before and one month after vaccinatioin. The immunogenicity and safety of both experimental and control groups will be compared and the data be analyzed.

To evaluate the safety and immunogenicity of simultaneously immunization of 23-valent pneumococcal polysaccharide vaccine (PPV23) and quadrivalent inactivated influenza vaccine (IIV4) , we design this randomized, parallel controlled study . 1224 subjects are divided into 3 groups, including 1 experimental group and 2 control groups (control group A and B), each group includes 408 subjects respectively.

Each 408-subject group is divided again into 4 age-based subgroups: ① 3-8 years old; ② 9-18 years old; ③ 19-49 years old ; ④ over 50 years old; each subgroup includes 102 subjects respectively.

408 subjects from experimental group will be simultaneously administrated with one dose of IIV (0.5 ml) and one dose of PPV23 (0.5 ml). Blood samples are collected before vaccination and one month (30 days) later.

408 subjects from control group A will be only administrated with one dose of IIV (0.5 ml). Blood samples are collected before vaccination and one month (30 days) later.

408 subjects from control group B will be only administrated with one dose of PPV23 (0.5 ml). Blood samples are collected before vaccination and one month (30 days) later.

To evaluate the immunogenicity, we will detect and compare the neutralization antibody levels, the seroprotection rates, and antibody geometric mean concentrations. The safety of all groups will be monitored as well.

Inclusion Criteria:

• subjects aged no younger than 3 years old on the day of recruitment;
• with valid informed consent signed by parent(s) or guardian(s);
• parent(s) or guardian(s) are able to attend all scheduled appointments and comply with all study instructions;
• subjects have not received any seasonal influenza vaccine or pneumonia vaccine before;
• axillary temperature ≤37.0℃

Exclusion Criteria:

• subject who has a medical history with hypersensitiveness, eclampsia, epilepsy, cerebropathia or neurological illness;
• allergic to any ingredient of vaccine or with allergy history to any vaccine;
• subjects with immunodeficency or suspected impairment of immunologic function (e.g. caused by HIV), or subjects are in the process of immunosuppressor therapy(taking orally injecting of steroid hormone);
• administration of immunoglobulins within 30 days prior to this study;
• acute febrile disease(temperature ≥ 37.0°C) or infectious disease;
• have a clearly diagnosed history of thrombocytopenia or other coagulopathy, which might cause contraindications for subcutaneous injection;
• any serious chronic illness, acute infectious diseases, or respiratory diseases; severe cardiovascular disease, liver and kidney diseases or diabetes mellitus with complications;
• any kind of infectious, purulent, or allergic skin diseases;
• pregnant women and breastfeeding women;
• inoculated with any vaccine within 14 days of the study;
• any other factor that makes the investigator determines the subject is unsuitable for this study.