To explore a bridging index for the effectiveness of the clinical trial with Nasal Spray Lyophilized Live Attenuated Influenza Vaccine

With a randomized, blind, parallel placebo-controlled design, to screen the susceptible individuals aged 3~59 years old whose titers of either of Hi antibody level of H1N1, H3N2 or B are not higher than 1:10 prior immunization , in which all persons are to be assigned into the two subgroups (aged 3~17 and 18~59 years old) with radio of 1:1, individually. All persons of each age subgroups are to be randomly assigned into the two groups (vaccine or placebo group) with th radio of 2:1 via intranasal injection of one dose of the study vaccine or placebo. The blood samples are to be collected prior immunisation and on the 21st day post immunisation, individually, the nasopharyngeal swab samples are also to be done prior immunisation and on the 10th day and 21st day post immunisation, individually, and the levels of serum HI antibody and mucous sIgA antibody are to be compared between the two groups, respectively.

Inclusion Criteria:

1. healthy volunteer aged 3~59 years old；
2. no vaccination with any influenza vaccine within the past year；
3. no catching any influenza or flu like symptoms （axillary temperature ≥ 38℃， accompanied by cough or sore throat ）；
4. influenza susceptible individual（any serum Hi antibody level of H1N1, H3N2 and B≦1:10）；
5. with informed consent obtained from the volunteer and / or guardian；
6. willing of volunteers and / or guardians to comply with the requirements of the clinical trial protocol.

Exclusion Criteria:

1. Known allergy individual to any ingredient of this product, including egg protein, subsidiary material and/or gentamycin sulfate;
2. patients with acute disease, severe chronic disease, acute attack of chronic disease and/or fever (axillary temperature ≥ 37.3℃ on the day of immunisation);
3. pregnancy (enquire);
4. patients with Leigh syndrome treated with aspirin or aspirin containing drugs;
5. patients with immunodeficiency or receiving immunosuppressive therapy;
6. patients with uncontrolled epilepsy and other progressive nervous system diseases, with a history of Guillain Barre syndrome;
7. patients with rhinitis or other nasal abnormalities judged by clinicians that may affect vaccination or sample collection;
8. accept any immunoglobulin and / or any blood products within 3 months, or plan to use them during the study (until post immunization blood sample collection);
9. .taking anti influenza drugs in the past 48 hours;
10. .any situation that the researchers believe may affect the study.