A Study on the Immune Response and Safety of Various Potencies of an Investigational Chickenpox Vaccine Compared With a Marketed Chickenpox Vaccine, Given to Healthy Children 12 to 15 Months of Age

Inclusion Criteria

• Healthy participants as established by medical history and clinical examination before entering into the study.
• A male or female between, and including, 12 and 15 months of age (i.e., from his/her 1 year birthday until the day before age of 16 months) at the time of the administration of the study interventions.
• Written informed consent obtained from the parent(s)/legally authorized representative(s) of the participant prior to performance of any study-specific procedure.
• Participants' parent(s)/legally authorized representative(s), who, in the opinion of the investigator, can and will comply, with the requirements of the protocol (e.g., completion of Electronic Diaries, return for follow-up visits).
• Only for US participants and participants in countries where pneumococcal conjugate vaccine is recommended at 12-15 months of life as per national immunization schedule: Participants who previously received the primary series of pneumococcal conjugate vaccine in their first year of life with the last dose at least 60 days prior to study entry.

Exclusion Criteria

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 varicella.
• Recurrent history of or uncontrolled neurological disorders or seizures.
• Participant with history of SARS-CoV-2 infection 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 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 interventions 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, or equivalent. 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 against measles, mumps, rubella, hepatitis A, and/or varicella virus.

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 varicella.
• Recurrent history of or uncontrolled neurological disorders or seizures.
• Participant with history of SARS-CoV-2 infection 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 Da