Phase II Study to Investigate the Kinetics of the Immune Response Generated by Influenza Virus Vaccine.

Inclusion Criteria: * Subjects had to have been at least 18 years of age and less than 65 years of age at the time informed consent was obtained; * Women of child-bearing potential had to use reliable methods of hormonal and/or nonhormonal contraception (which includes cervical cap, diaphragm, condoms with spermicide or IUD) during sexual intercourse throughout the entire study period; a negative urine pregnancy test (with detection limit of less than or equal to 25mIU/mL) no more than 24 hours prior to vaccine administration; and agreed to avoid pregnancy during participation in the study. A urine pregnancy test was also conducted at the completion of study participation. Females who were surgically sterile at time of enrollment were not required to undergo pregnancy testing. * who were determined by medical history, physical examination and clinical judgement to be eligible for the study. * who provided written informed consent after the nature of the study has been explained; * who were available for one month duration of the trial (from enrollment to study completion); * who could be reached by study staff for the post-vaccination contact \[telephone, clinic or home visit\]. Exclusion Criteria: * who were perceived to be unavailable or difficult to contact for evaluation or study visits during the study period; * with a known or suspected disease of the immune system or those receiving immunosuppressive therapy, including systemic corticosteroids and intranasal steroids; or cytotoxic agents; * who had an immunosuppressed or an immunocompromised individual living in the same household; * who had a documented history of hypersensitivity to egg or egg protein or any other component of the study vaccine or placebo; * who received any commercially-available or investigational injected influenza vaccine in the 6 months prior to enrollment, or a non-study influenza vaccine since enrollment; * who previously received an intranasally administered influenza vaccine; * who had any medical conditions that, in the opinion of the investigator, might interfere with interpretation of the study results;