A single center, stratified, randomized and double-blind phase IV clinical trial is to be conducted in healthy elders (equal to or more than 61 years), adults (18-60 years), adolescents (12-17 years) and children (3-11 years) to evaluate the safety and immunogenicity of Sinovac's split-virion or whole-virion novel influenza A (H1N1) vaccines.

Inclusion Criteria:

1. Healthy male or female aged 3 and older
2. Be able to show legal identity card for the sake of recruitment
3. Volunteers or their guardians are able to understand and sign the informed consent

Exclusion Criteria:

1. Cases, cured cases and close contact of influenza A (H1N1) virus

2. Women of pregnancy, lactation or about to be pregnant in 60 days

3. Subject that has a medical history of any of the following: allergic history, or allergic to any ingredient of vaccine, such as egg, egg protein, etc

4. Serious adverse reactions to vaccines such as anaphylaxis, hives, respiratory difficulty, angioedema, or abdominal pain

5. Autoimmune disease or immunodeficiency

6. Asthma that is unstable or required emergent care, hospitalization or intubation during the past two years or that required the use of oral or intravenous corticosteroids

7. Diabetes mellitus (type I or II), with the exception of gestational diabetes

8. History of thyroidectomy or thyroid disease that required medication within the past 12 months

9. Serious angioedema episodes within the previous 3 years or requiring medication in the previous two years

10. Bleeding disorder diagnosed by a doctor (e.g. factor deficiency, coagulopathy, or platelet disorder requiring special precautions) or significant bruising or bleeding difficulties with IM injections or blood draws

11. Active malignancy or treated malignancy for which there is not reasonable assurance of sustained cure or malignancy that is likely to recur during the period of study

12. Seizure disorder other than:

    • Febrile seizures under the age of two years old
    • Seizures secondary to alcohol withdrawal more than 3 years ago, or
    • A singular seizure not requiring treatment within the last 3 years

13. Asplenia, functional asplenia or any condition resulting in the absence or removal o the spleen

14. Guillain-Barre Syndrome

15. Any history of immunosuppressive medications or cytotoxic medications or inhaled corticosteroids within the past six months (with the exception of corticosteroid nasal spray for allergic rhinitis or topical corticosteroids for an acute uncomplicated dermatitis)

16. History of any blood products or seasonal influenza vaccine administration within 3 months before the dosing

17. Administration of any other investigational research agents within 30 days before the dosing

18. Administration of any live attenuated vaccine within 30 days before the dosing

19. Administration of subunit or inactivated vaccines, e.g., pneumococcal vaccine, or allergy treatment with antigen injections, within 14 days before the dosing

20. Be receiving anti-TB prophylaxis or therapy currently

21. Axillary temperature > 37.0 centigrade at the time of dosing

22. Psychiatric condition that precludes compliance with the protocol:

    • Past or present psychoses
    • Past or present bipolar disorder requiring therapy that has not been well controlled on medication for the past two years
    • Disorder requiring lithium
    • Suicidal ideation occurring within five years prior to enrollment

23. Any medical, psychiatric, social condition, occupational reason or other responsibility that, in the judgment of the investigator, is a contraindication to protocol participation or impairs a volunteer's ability to give informed consent