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.
Phase 1 trials primarily test safety and dosing in a small number of participants (typically 20–100). Results do not yet speak to efficacy. FDA approval is typically many years away from this stage.
Enrollment is complete. The trial is in its follow-up or data collection phase — a readout may occur on or near the primary completion date.
Pfizer Inc (PFE) is the sponsoring company for this trial. BiotechSign currently grades this company F (33/100) based on composite catalyst signals across its full pipeline. This trial is one data point in that overall catalyst picture.