The primary study objectives are:
* To demonstrate that a 2-dose regimen of ProQuad® manufactured with recombinant Human Albumin (rHA) administered at a 3-month interval to healthy children of 11 months of age at the time of Dose 1 is as immunogenic as in healthy children of 12 months of age at the time of Dose 1.
* To demonstrate that a 2-dose regimen of ProQuad® rHA administered at a 3-month interval to healthy children of 9 months of age at the time of Dose 1 is as immunogenic as in healthy children of 12 months of age at the time of Dose 1.
* To demonstrate that a 2-dose regimen of ProQuad® rHA administered at a 3-month interval to healthy children of 11 months of age and 9 months of age at the time of Dose 1 is well-tolerated compared to children of 12 months of age at the time of Dose 1.
The first primary hypothesis was that a 2-dose regimen of ProQuad® rHA, administered at a 3-month interval to children of 11 months of age, would be non-inferior in terms of antibody response rates to measles, mumps, rubella, and varicella at Day 42 following Dose 2, to the same regimen in children of 12 months of age at the time of Dose 1.
If the first primary hypothesis was demonstrated, the second primary hypothesis was that a 2-dose regimen of ProQuad® rHA, administered at a 3-month interval to children of 9 months of age, would be non-inferior in terms of antibody response rates to measles, mumps, rubella, and varicella at Day 42 following Dose 2, to the same regimen in children of 12 months of age at the time of Dose 1.
The secondary study objectives are:
* To describe the antibody titres to measles, mumps, rubella and varicella at Day 42 following Dose 1 and Dose 2 of ProQuad® rHA administered to healthy children from 9 months of age.
* To evaluate the safety profile of Dose 1 and Dose 2 of ProQuad® rHA administered to healthy children from 9 months of age.