The purpose of this study is to learn about the safety and tolerability of a pneumococcal vaccine in adults. Participants will receive either: * an experimental PG4 vaccine * a PG4 vaccine comparator * a standard 20vPnC vaccine comparator * placebo. A placebo does not have any medicine in it but looks just like the study medicine. Participants will take part in this study for up to 18 months depending on which group they are assigned to. During this time, the participants will receive up to two doses of study vaccine or comparator and take part in follow-up visits. At these clinic visits, participants will be asked if any side effects were experienced. The participants will also have to give blood samples during clinic visits.
See this in plain English?
AI-rewrites the medical criteria so a patient or caregiver can understand them. Always confirm with the trial site.
Percentage of participants reporting prespecified local reactions after each dose.
Timeframe: Within 7 days after each study intervention.
Percentage of participants reporting prespecified systemic reactions after each dose.
Timeframe: Within 7 days after each study intervention.
Percentage of participants reporting adverse events.
Timeframe: From signing of the ICD to 1 month after last study intervention.
Percentage of participants reporting serious adverse events.
Timeframe: From signing of the ICD to 6 months after the last study intervention.
Percentage of participants reporting serious adverse events.
Timeframe: From signing of the ICD to 12 months after the last study intervention.
Percentage of participants with abnormal hematology and chemistry laboratory values.
Timeframe: Within 2 weeks after each study intervention.