Live Attenuated freeze-dried Influenza Vaccine has been licensed for use in 2020 (Approval No.S20200002), the sponsor of this research submitted an new application for non freeze-dried Live Attenuated Influenza Vaccine in 2021. The main objective of phase two trail is to evaluate the immunogenicity of LAVI (non freeze- dried). The secondary objective is to evaluate the safety of LAVI (non freeze- dried).

Totally 2520 health people aged 3-59 years old will be divided into two age group, containing 1260 in 18-59 years old and 1260 in 3-19 years old. All subjects will receive vaccination either LAVI(non freeze- dried), LAVI(freeze- dried) or placebo in a ratio of 2:2:1.

All subjects will be collected any adverse events within 30 days and any serious adverse events within 6 months for safety evaluation. All subjects will be collected blood sample and nasopharyngeal swab for immunogenicity evaluation.

Inclusion Criteria:

• Healthy volunteers aged in 3-59 years old
• Had not received vaccination of Influenza vaccine in the past one year
• Had not infected with Influenza virus
• This trail has been agreed by volunteers or his/her legal guardian
• Volunteers or his/her legal guardian will fellow this trail protocol

Exclusion Criteria:

• People with fever before vaccination, temperature higher than 37.0 #
• Females in suckling period, pregnancy (pregnancy test positive) or prepared to be pregnant
• People given whole blood, plasma or immunoglobulin therapy within 3 months before vaccination
• According to judgement of researchers, the subjects have any other factors that are not appropriate for this clinical trials
• Acute infectious disease or acute attack of chronic disease before inoculation
• People get any vaccine within 14 days before the trial
• People in immune deficiency or diagnosed with congenital or acquired immunodeficiency, people with immunosuppressive therapy in the past six months
• People with epilepsy or a history of mental illness

The design of this trail is based on random, one-blind, placebo control. The subjects will not know the masking status, unless the specific subjects who required treatment for serious adverse events .