This study evaluates the safety of freeze-dried live attenuated influenza vaccine for intranasal administration in chinese adults aged 3 years and older.80 subjects will be divided into 2 groups, including 18 years and older and 3-17 years old. Subjects in each groups will randomly receive one dose of influenza vaccine or placebo in a 3:1 ratio.

Inclusion Criteria:

1. Healthy subjects more than 3 years
2. Guardian and/or subjects aged at least 10 subjects can be informed consent, and sign a written Informed Consent Form.
3. Subjects, Guardians and his family can obey the demands of the scheme .
4. Axillary temperature less than 37℃

Exclusion Criteria:

1. Subjects with flu or infected with flu within 3 months.
2. Subjects have a vaccine allergies, allergic to any kind of composition in experimental vaccine, such as eggs, ovalbumin etc.
3. Subjects have serious side effects to vaccine, such as allergy, urticaria, skin eczema, dyspnea, angioneurotic edema or abdominal pain.
4. Subjects have symptoms of acute infection within a week.
5. Subjects have autoimmune disease or immune function defect, Subjects have used immunosuppressive therapy, cytotoxic treatment or inhaled corticosteroids in the past 6 months.
6. Subjects have congenital malformations, developmental disorder or serious chronic diseases( such as Down's syndrome, diabetes, Sickle cell anemia or nerve system disease)
7. Subjects have asthma unstable that need emergency treatment, hospitalization, intubation, oral or intravenous corticosteroid in the past 2 years.
8. Subjects have medical history or family history of convulsions, seizures, encephalopathy and psychiatric disease.
9. Alienia, functional asplenia, and alienia or splenectomy in any situation.
10. Serious neurological disorders such as Green Barry syndrome.
11. Subjects have received blood products or immunoglobulin products within 3 months before experimental vaccine inoculated.
12. Subjects have received other study drug in the past month or received live vaccine, subunit vaccine or inactivated vaccine.
13. The indicators of blood test or urine test do not conform to the inclusion criteria.
14. Subjects have received allergy treatment in in the past 14 days.
15. Subjects are receiving anti-tuberculosis treatment.
16. Subjects have inoculated flu vaccine in the flu reason.
17. Axillary temperature is more than 37℃ before vaccination.
18. Subjects are pregnant or plan to become pregnant
19. Subjects are participate in other clinical trials.
20. Any factors unsuitable for clinical trail at the discretion of the investigator.