The purpose of this study is to determine the efficacy, safety and tolerability of the liquid formulation of CAIV-T against culture confirmed influenza illness in adults aged 60 years and older. In addition this study aims to demonstrate superiority of CAIV-T when compared with placebo and the effect on economic resources.

To evaluate the efficacy over 1 year against culture-confirmed influenza-illness caused by community-acquired subtypes antigenically similar to those contained in the vaccine, in adults aged ≥ 60 years at enrollment, of 1 dose of an intranasally-administered (IN) liquid formulation of influenza virus vaccine, trivalent, types A and B, live, cold-adapted (CAIV-T; Wyeth, Marietta, PA, USA) compared with saline placebo.

Inclusion Criteria:

• who are and aged at least 60 years or older at the time of enrollment;
• who are determined by medical history, physical examination and clinical judgement to be eligible for this study. Subjects with stable pre-existing disease, defined as disease not requiring change in therapy or hospitalization within 12 weeks before receipt of study vaccination will be eligible.
• who have provided written informed consent after the nature of the study has been explained;
• who, will be available for duration of the trial (from enrollment to approximately November 30, 2001); who can be reached by study staff for the post-vaccination and weekly surveillance contacts [telephone, clinic or home visit].

Exclusion Criteria:

• who are perceived to be unavailable or difficult to contact for evaluation or study visits during the study period;
• who are a resident of a nursing home or long-term care facility or other institution receiving skilled or semi-skilled nursing care (refer to study manual). An ambulatory subject who is a resident of a retirement home or village is eligible for the trial.
• With evidence of dementia or other severe cognitive impairment based on Mini Mental State Examination (MMSE) scores (refer to study manual).
• with a known or suspected disease of the immune system or those receiving immunosuppressive therapy, including systemic corticosteroids; or cytotoxic agents;
• who received any blood products, including immunoglobulin, in the period from six months prior to vaccination through to the conclusion of the study;
• have an immunosuppressed or an immunocompromised individual living in the same household;
• with a documented history of hypersensitivity to egg or egg protein or any other component of the study vaccine or placebo;
• who were administered any live virus vaccine within one month prior to enrollment or expected to receive another live virus vaccine within one month of vaccination in this 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;
• who, received a dose of influenza treatment (commercial or investigational) one month prior to enrollment. The prophylactic use of influenza antivirals is not permitted.
• who receive any influenza vaccine in the 6 months to enrollment, or a non-study influenza vaccine since enrollment;
• with any medical conditions that in the opinion of the investigator might interfere with interpretation of the study results; Note: A pregnant household member is not considered a contraindication to enrollment