Inclusion Criteria:  ≥18 years old when enrolled; Participants signing the informed consent; Being able to participate in all planned follow-ups and accomplish all research procedures including completing a diary card and coming back for interview; Having not been administered any pneumonia vaccine or COVID-19 vaccine, and having not been administered an influenza vaccine in the current season before enrollment; ≥14 days from the most recent vaccination; Before enrollment, the body temperature is ≤37.0C as confirmed by medical history and clinical examination.  Exclusion Criteria:  Having a history of COVID-19 or a positive nucleic acid test for COVID-19; Having a history or a family history of allergy, convulsion, epilepsy, brain disease, or mental illness; Being allergic to any component of vaccines, or having a history of severe allergic reaction to any vaccine; Having immunodeficiency disorder, during treatment of malignant tumor, having immunodeficiency induced by immunosuppressants (oral steroid hormones) or HIV, or having a family member with close contact who suffers from congenital immune disorder; Having injection of non-specific immunoglobulin within 1 month prior to enrollment; Having acute febrile illness or communicable disease; Having a history of confirmed thrombocytopenia or other coagulation disorders, which may cause contraindications for a subcutaneous injection; Having severe chronic disease or acute exacerbation of chronic disease, or having uncontrolled hypertension or diabetes; Having various infectious, pyogenic, or allergic skin diseases; Women in pregnancy or lactation or participants who plan for a baby within 3 months after vaccination should delay the vaccination; Having any condition that may affect trial assessment as determined by researchers.  Exclusion criteria for the second dose:  Having any serious adverse event related to the first dose vaccination; After vaccination, having systemic adverse reaction or allergic reaction with a severity of grade 3 or higher as determined by researchers; Having a newly emerging condition that meets the exclusion criteria for the first dose; Having any condition that may affect trial assessment as determined by researchers.