A Study on the Immune Response and Safety of a Combined Measles, Mumps, Rubella, Chickenpox Vaccine Compared to a Marketed Combined Vaccine, Given to Healthy Children 4 to 6 Years of Age

Medical Conditions

History of any reaction or hypersensitivity likely to be exacerbated by any component of the study interventions including hypersensitivity to neomycin or gelatin.

Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination (no laboratory testing required).

Hypersensitivity to latex.

Major congenital defects, as assessed by the investigator.

History of measles, mumps, rubella, or varicella disease.

Recurrent history of or uncontrolled neurological disorders or seizures.

Acute disease at the time of enrollment. Acute disease is defined as the presence of a moderate or severe illness with or without fever. Fever is defined as body temperature \>=38.0 degrees Celsius (°C) (100.4 degrees Fahrenheit \[°F)\] by any age-appropriate route. All study interventions can be administered to participants with a minor illness such as diarrhea, mild upper respiratory infection without fever.

Participant with history of coronavirus disease 2019 (COVID-19) who is still symptomatic.

Any other clinical condition that, in the opinion of the investigator, might pose additional risk to the participant due to participation in the study.

Prior and Concomitant Therapy

Use of any investigational or non-registered product (drug, vaccine, or medical device) other than the study interventions during the period beginning 30 days before the dose of study interventions (Day -29 to Day 1), or their planned use during the study period.

Chronic administration (defined as more than 14 days in total) of immunosuppressants or other immune-modifying drugs during the period starting 90 days prior to the study intervention administration. For corticosteroids, this will mean prednisone equivalent \>= 0.5 mg/kg/day or 20 mg/day whichever is the maximum dose for pediatric participants. Inhaled and topical steroids are allowed.

Administration of immunoglobulins and/or any blood products or plasma derivatives during the period starting 180 days before the dose of study interventions or planned administration during the study period.

Administration of long-acting immune-modifying drugs at any time during the study period (e.g., infliximab).

Previous vaccination with a second dose of varicella-containing vaccine or measles-, mumps-, rubella-containing vaccine.

Administration or planned administration of a vaccine not foreseen by the study protocol in the period starting 30 days before the dose and ending at 43 days after the dose of study interventions administration\* (Visit 3), with the exception of:

* inactivated influenza (flu) vaccine which may be given at any time during the study and administered at a different location than the study interventions and,

* routinely recommended licensed childhood DTPa-containing vaccines which can preferably be co-administered according to the local immunization practices of the participating country.

Any other age-appropriate vaccine may be given starting at Visit 3 and anytime thereafter.

* In case an emergency mass vaccination for an unforeseen public health threat (e.g., a pandemic) is recommended and/or organized by public health authorities outside the routine immunization program, the time period described above can be reduced if necessary for that vaccine, provided it is used according to the local government recommendations and that GSK/IQVIA is notified accordingly.

Prior/Concurrent Clinical Study Experience

Concurrently participating in another clinical study, at any time during the study period, in which the participant has been or will be exposed to an investigational or a non-investigational intervention (drug/invasive medical device).

Other Exclusions

Child in care.

Any study personnel's immediate dependents, family, or household members.

Participants with the following high-risk individuals in their household:

* Immunocompromised individuals

* Pregnant women without documented history of varicella.

* Newborn infants of mothers without documented history of varicella.

* Newborn infants born \<28 weeks of gestation.

What this study is about