To assess the safety of a vaccine in healthy adults prior to the release of the trivalent vaccine (FluMist).

The primary study objective is to assess the safety of a monovalent vaccine of a new 6:2 reassortant in healthy adults prior to the release of the trivalent vaccine (FluMist). Safety will be demonstrated by similar fever rates (oral temperature ≥101°F) in vaccine and placebo recipients.

Inclusion Criteria:

• 18-64 years of age (not yet reached their 65th birthday);
• In good health;
• Available by telephone;
• Ability to understand and comply with the requirements of the protocol; and
• Signed informed consent.

Exclusion Criteria:

• Any condition, other than age, for which the inactivated influenza vaccine is indicated, including: chronic disorders of the pulmonary or cardiovascular systems, including asthma; chronic metabolic diseases (including diabetes mellitus) renal dysfunction, or hemoglobinopathies which required regular medical follow-up or hospitalization during the proceeding year;
• Acute febrile (>100.0°F oral) illness or clinically significant respiratory illness within the 14 days prior to enrollment;
• Hypersensitivity to egg or egg protein;
• Signs or symptoms of any immunosuppressive or immune deficiency disease, including HIV infection, or ongoing immunosuppressive therapy; or an immunosuppressed individual living in the same household;
• Participation in another investigational trial within one month prior to enrollment or expected enrollment in another investigational trial during this study; and
• Any condition that in the opinion of the investigator, might interfere with the vaccine evaluation.