Study of a 4-Dose Regimen of a 21-valent Pneumococcal Conjugate Vaccine in Healthy Infants From Approximately 2 Months of Age

This study is a Phase 3, randomized, modified double-blind study which aims to measure whether PCV21 vaccine (investigational pneumococcal conjugate vaccine) is safe and can help the body to develop germ-fighting agents called "antibodies" (immunogenicity) compared with 20-valent pneumococcal vaccine (Prevnar 20, licensed pneumococcal conjugate vaccine) when they are administered with routine pediatric vaccines in infants aged from approximately 2 months (42 to 89 days). The study duration per participant will be up to approximately 19 months. The study vaccines (either PCV21 or 20-valent pneumococcal vaccines) will be administered at approximately 2, 4, 6 and 12 to 15 months of age. Routine pediatric vaccines will be given at the same timepoints. There will be 6 study visits: -Visit (V)01, V02 separated from V01 by 60 days, V03 separated from V02 by 60 days, V04 separated from V03 by 30 days, V05 at 12 months of age until 15 months of age, V06 separated from V05 by 30 days.

Inclusion Criteria: * Aged 42 to 89 days on the day of inclusion * Participants who are healthy as determined by medical evaluation including medical history and physical examination * Born at full term of pregnancy (≥ 37 weeks) and with a birth weight ≥ 2.5 kg or born after a gestation period above 28 (\> 28 weeks) through 36 weeks with a birth weight ≥ 1.5 kg, and in both cases medically stable as assessed by the investigator Exclusion Criteria: Participants are excluded from the study if any of the following criteria apply: * Known or suspected congenital or acquired immunodeficiency; or receipt of immunosuppressive therapy, such as anti-cancer chemotherapy or radiation therapy; or long-term systemic corticosteroid therapy * History of microbiologically confirmed Streptococcus pneumoniae infection or disease * Any contraindication to the routine pediatric vaccines being administered in the study * History of seizure or significant stable or progressive neurological disorders such as infantile spasms, inflammatory nervous system diseases, encephalopathy, cerebral palsy * Known systemic hypersensitivity to any of the study interventions components, or history of a life-threatening reaction to the study interventions used in the study or to a product containing any of the same substances * Laboratory-confirmed or known thrombocytopenia, as reported by the parent/legally acceptable representative (LAR), contraindicating intramuscular (IM) injection * Bleeding disorder, or receipt of anticoagulants in the 3 weeks preceding inclusion, contraindicating IM injection * Chronic illness that, in the opinion of the investigator, is at a stage where it might interfere with study conduct or completion * Moderate or severe acute illness/infection (according to investigator judgment) or febrile illness (temperature ≥ 38.0°C \[≥ 100.4°F\]) on the day of study intervention administration. A prospective participant should not be included in the study until the condition has resolved or the febrile event has subsided. * Receipt of any vaccine in the 4 weeks preceding the study intervention administration or planned receipt of any vaccine in the 4 weeks following the study intervention administration, except for US licensed influenza vaccination, which may be received at least 2 weeks before or 2 weeks after any study vaccination. This exception includes monovalent pandemic influenza vaccines and multivalent influenza vaccines, as applicable per local recommendations. * Previous vaccination against S. pneumoniae * Previous vaccination against the following antigens: diphtheria, tetanus, pertussis, Haemophilus influenzae type b, and poliovirus * Receipt of more than 1 dose of hepatitis B vaccine * Receipt of immune globulins, blood or blood-derived products since birth * Participation at the time of study enrollment (or in the 6 weeks preceding the first study intervention administration) or planned participation during the present study period in another clinical study investigating a vaccine, drug, medical device, or medical procedure Note: The above information is not intended to contain all considerations relevant to a potential participation in a clinical trial.