A Trial on the Efficacy, Safety and Immunogenicity of Live-Attenuated Influenza Vaccine (LAIV)

This study is a Multicenter, Randomized, Double-Blind, Placebo-Controlled, Phase Ⅲ Trial to evaluate the efficacy, safety and immunogenicity of a single dose of Live-Attenuated influenza Vaccine(LAIV) among healthy children and adolescents aged 3-17 years old. The subjects will be randomized in a 1:1 ratio of LAIV to placebo. Each subject will be vaccinated with a single dose of LAIV or Placebo. For evaluation of efficacy, subjects meeting the protocol-defined clinical case definition the 14th day post-vaccination will have a nasal swab collected for testing by RT-PCR or virus culture for evidence of influenza virus infection. All adverse events will be collected 30 minutes, 0-30 days after vaccination and all serious adverse events during the entire trial period. Blood samples will be collected from a part of subjects before vaccination and at the 30th day after immunization. Serum samples will be centrifuged for detection of antibodies to H1N1, H3N2, and influenza B.

Inclusion criteria

• Healthy children and adolescents aged 3-17 years old.
• Informed consent obtained and signed by subjects or legal guardians prior to screening. Children or adolescents aged 10-17 yrs need sign informed consent by themselves.
• Willing to participate for the planned duration of the study, including availability for follow-up.

Exclusion criteria

• Any investigational or unregistered product (drug, vaccine or device) was used within 30 days, or planned to be used during the trial.
• have been vaccinated with any influenza vaccine within 6 months, or plan to be vaccinated during the trail.
• Immunosuppressive agents or other immunomodulatory drugs (defined as continuous use for more than 14 days) were used over a 3-month period.
• Immunoglobulins and / or any blood products were used within 3 months, or planned to be used before blood collection.
• History of Guillain-Barré syndrome; History of hypersensitivity to any component of the LAIV, including egg or egg products.
• Severe allergic reactions after vaccination (including anaphylactic shock, allergic laryngeal edema, allergic purpura, local allergic necrosis).
• Acute diseases , infections or febrile diseases (axillary temperature ≥37.1℃) on the day of vaccination.
• Obvious coagulation dysfunction or History of anticoagulant therapy
• Aspirin is being used(Salicylates are a potential risk factor for Reye syndrome)
• Known or suspected immune deficiency diseases or immunosuppressed
• Heart disease, respiratory diseases (including severe rhinitis, nasal deformities, polyps, etc.), liver disease, kidney disease, mental disorders, chronic infections etc.