The purpose of this study is to learn about the safety of the 20-valent pneumococcal conjugate vaccine (20vPnC) among adults, children, and infants, as well as the immunogenicity of 20vPnC among infants and children under 2 years of age in China. This vaccine will be given as per the age-specific dosing schedules among healthy adults, children and infants in China.

This study is seeking healthy participants of 6 groups:

• Group 1: Adults ≥18 to <50 years of age
• Group 2: Children ≥2 to <6 years of age
• Group 3: Children ≥12 months to <2 years of age
• Group 4: Infants ≥7 to <12 months of age
• Group 5: Infants ≥42 to ≤98 days of age
• Group 6: Infants ≥42 to ≤98 days of age

All participants in Group 1 to 5, in this study will receive 20vPnC as per the age-specific dosing schedules:

• Group 1: participants will receive 1 dose of 20vPnC.
• Group 2: participants will receive 1 dose of 20vPnC.
• Group 3: participants will receive 2 doses of 20vPnC. Dose 2 will be given 56 to 70 days after Dose 1.
• Group 4: participants will receive 3 doses of 20vPnC. Dose 2 will be given 28 to 56 days after Dose 1, and Dose 3 will be given at 365 to <455 days of age and at least 56 days after Dose 2.
• Group 5: participants will receive 4 doses of 20vPnC. Dose 2 will be given 42 to 63 days after Dose 1, and Dose 3 should be given 42 to 63 days after Dose 2, and Dose 4 should be given at 365 to <455 days of age.

Participants in Group 6 will be randomized in a 1:1 ratio to received either 20vPnC or 13vPnC:

- Group 6: participants will receive 4 doses of 20vPnC or 13vPnC. Dose 2 will be given 42 to 63 days after Dose 1, and Dose 3 should be given 42 to 63 days after Dose 2, and Dose 4 should be given at 365 to <455 days of age.

The study will look at the experiences of people receiving the study vaccine. The study will also look at the immune response of some people receiving the study vaccine. This will help decide if the study vaccine is safe.

The total duration of taking part in the study from each group is:

• Participants in Group 1 and Group 2 will take part for about 6 months, with 6 visits.
• Participants in Group 3 will take part for about 8 months, with 9 visits.
• Participants in Group 4 will take part for about 12 months, with 8 visits.
• Participants in Group 5 and 6 will take part for about 16 to 19 months, with 11 visits.

Key inclusion criteria:

• Male or female participants:

  • Adults ≥18 to <50 years of age
  • Children ≥2 to <6 years of age
  • Children ≥12 months to <2 years of age
  • Infants ≥7 to <12 months of age
  • Infants ≥42 to ≤98 days of age

• Healthy participants determined by clinical assessment and clinical judgment, to be eligible for the study.

Key exclusion criteria:

• History of severe adverse reaction associated with a vaccine and/or severe allergic reaction (eg, anaphylaxis) to any component of the study intervention, or any diphtheria toxoid-containing vaccine.
• History of microbiologically proven invasive disease caused by S pneumoniae.
• Congenital, functional, or surgical asplenia.
• Previous vaccination with any licensed or investigational pneumococcal vaccine, or planned receipt during study participation.
• Determined as not eligible by the investigator based on the participant's past and present health condition(s), medication(s) and treatment(s).

Please refer to the study contact for further eligibility details.

Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.

This is an open label study. Participant, investigators, and sponsor will be unblinded to the participant's assigned study intervention.