This study is for people aged 50 and above who had a pneumonia vaccine before. It checks if a new vaccine, called VAX-31, is safe and helps your body fight germs. *Pneumococcal* vaccines help protect against types of bacteria that can cause lung infections. The study includes people who had a pneumonia vaccine at least one year ago. If it's a specific type called PCV21, it should be six months ago.
- Length of Study: Participants will have follow-up visits through the last study visit.
- Participation Requirements: You need a device with internet for an online diary and to give blood samples.
- Exclusion Criteria: You cannot join if you had certain illnesses, a recent vaccine, or if you're pregnant or nursing.
Being part of this study means you might help find a better pneumonia vaccine for older adults. Participants need to be in good health or have stable conditions and must not have certain illnesses or conditions that can affect the study. If you're pregnant or planning to be, you cannot join. Participants will receive the vaccine and be monitored for safety and effectiveness.