MMR and MMRV Vaccines: Effect of Age at First Dose on Safety and Immunogenicity of the Measles Component.

Inclusion Criteria: * Healthy male or female subject between 11 to 22 months at the time of first vaccination. * Written informed consent obtained from the parent/guardian of the subject. Exclusion Criteria: * History of previous measles, mumps, rubella and/or varicella vaccination or disease or known exposure to any of these diseases within 30 days prior to the inclusion in the study. * Any confirmed or suspected immunosuppressive or immunodeficient condition, included the chronic administration (defined as more than 14 days) of immune-suppressants or other immune-modifying drugs within six months prior to the firs vaccine dose. * History of any neurologic disorders or seizures. * History of allergic diseases or reactions likely to be exacerbated by any component of the vaccines. * Planned administration of a vaccine not foreseen by the study protocol from 30 days prior to each vaccination until 42-56 days after each vaccination