A Multi-centered, Randomized, Controlled Study to Evaluate the Safety and Immunogenicity of Combined Immunization of 23-valent Pneumococcal Polysaccharide Vaccine (PPV23) and Quadrivalent Inactivated Influenza Vaccine (IIV4)
Subjects will be recruited and divided into 3 groups: Experimental Group (408 subjects): combined immunization of PPV23 and IIV4; Control Group A (408 subjects): IIV4 only; 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.