Inclusion Criteria:

• 12 to 15 months of age (not reached their 16th month birthday);
• In good health;
• Parent/guardian available by telephone or for home visits;
• Ability of the parent/guardian to understand and comply with the requirements of the protocol;
• Signed informed consent by parent/guardian; and
• Up to date with the primary series of recommended vaccines per standard clinic practice and local vaccine availability.

Exclusion Criteria:

• Previous known measles, mumps, rubella or varicella disease;
• Previous vaccination against measles, mumps, rubella or varicella disease;
• Hypersensitivity to egg or egg protein;
• Signs or symptoms of any immunosuppressive or immune deficiency disease or ongoing immunosuppressive therapy; or an immunosuppressed individual living in the same household;
• Acute febrile (>100.0oF [37.8°C] oral) illness or clinically significant upper respiratory illness within the 72 hours prior to enrollment;
• Use of aspirin (acetylsalicylic acid) or aspirin-containing products in the month prior to enrollment, or expected use of aspirin while enrolled in this study;
• Administration of any intranasal medication within two weeks prior to enrollment or expected receipt during this study;
• Administration of any live virus vaccine within one month prior to enrollment through 30 days after Visit 3;
• Administration of any inactivated vaccine within two weeks prior to enrollment through 30 days after Visit 3;
• Participation in another investigational trial within one month prior to enrollment or expected enrollment in another investigational trial during this study;
• Receipt of any blood product within three months prior to vaccination or expected receipt within the study duration; and
• Any condition which, in the opinion of the investigator, would interfere with the interpretation or evaluation of the vaccines.
• History of two or more episodes of medically attended wheezing illness by parent/guardian report.
• History of medically attended wheezing illness or bronchodilator medication use within four weeks of enrollment by parent/guardian report.