- The purpose of this study is to determine the efficacy of CAIV-T in a diverse Asian population aged from 6 months to less than 36 months, in tropical and temperate climates, against culture-confirmed influenza illness. In addition, the trial provides the opportunity to investigate the efficacy of CAIV-T over multiple influenza seasons, and to investigate the effect of CAIV-T on acute otitis media.

Inclusion Criteria:

• who are greater than or equal to 6 months and less than 36 months of age at the time of enrollment, and in good health as determined by medical history, physical examination, and clinical judgment;
• whose parent or legal guardian has provided written informed consent after the nature of the study has been explained;
• who, along with their parent or legal guardian, will be available for the duration of the study (24 months);
• whose parent/legal guardian can be reached by study staff for the post-immunization contacts [via telephone, clinic or home visits].

Exclusion Criteria:

• whose parents or caregiver are perceived to be unreliable or difficult to contact for evaluation or study visits during the study period;
• with any serious chronic disease (e.g., with signs of cardiac or renal failure or severe malnutrition), including progressive neurological disease;
• with Down's syndrome or other known cytogenetic disorders;
• with a known or suspected disease of the immune system or those receiving immunosuppressive therapy, including systemic corticosteroids;
• who received any blood products, including immunoglobulin, in the period from six months prior to vaccination through to the conclusion of the study;
• for whom there is intent to administer any other investigational vaccine or agent from one month prior to enrollment through to the conclusion of the study;
• with an immunosuppressed or compromised individual living in the same household;
• who, at any time prior to entry into this study, received a dose of any influenza vaccine (commercial or investigational);
• who were administered any live virus vaccine within one month prior to study vaccination or expected receipt of another live virus within one month of vaccination in this study;
• with a documented history of hypersensitivity to egg or egg protein, or any other component of the study vaccines or placebo;
• with a respiratory illness with wheezing within two weeks prior to enrollment;
• who received aspirin (acetylsalicylic acid) or aspirin-containing products in the two weeks prior to enrollment or for which use is anticipated during the study;
• with any medical conditions that in the opinion of the Investigator might interfere with interpretation of the study results; Note: A pregnant household member or day care provider is not considered a contraindication to enrollment.