This Phase 1, randomized, double-blind, third-party-unblinded study will be conducted at investigational sites in China. The purpose of the study is to learn about the safety and immune response of 20vPnC and 13vPnC in Chinese adults 50 years of age and older who did not receive any of pneumococcal vaccine in the past

The purpose of the study is to learn about the safety and immune response of 20vPnC and 13vPnC vaccines in Chinese adults. This study is seeking for participants who:

• are 50 years of age and older
• did not receive any of vaccines used to treat infections caused by the bacteria called Streptococcus pneumonia in the past.

The participants will be grouped by three age groups:

• Adults between 50 to 59 years of age
• Adults between 60 to 64 years of age
• Adults who are 65 years of age or above

All participants in this study will receive a single dose of 20vPnC or 13vPnC at study clinic. The study will look at the experiences of people receiving 20vPnC and 13vPnC. This will help decide if the study vaccine is safe.

The total duration of taking part in the study will be around 6 months, with 6 visits.

Key inclusion criteria:

1.Generally healthy adults including those with preexisting stable disease determined to be eligible based on clinical assessment, medical history and clinical judgment.

Key exclusion criteria:

1. History of microbiologically-proven invasive disease caused by Streptococcus pneumoniae
2. Previous vaccination with any licensed or investigational pneumococcal vaccine or planned receipt through study participation.

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.