This study is designed to find out how well the COVID-19 vaccine protects people 50 to 64, who don't have any serious health problems, compared to a group that receives a vaccine that doesn't contain an ingredient to protect against COVID-19 (placebo).

The study is designed to evaluate if the COVID-19 vaccine reduces COVID-19 disease as compared to placebo given to healthy adults 50 to 64 years of age. Approximately 25,500 participants will be randomly chosen to get either one dose of COVID-19 vaccine or of a placebo.

Key Inclusion Criteria

• People who are between 50 and 64 years old at their first appointment.
• People who are healthy and, based on their medical history and a doctor's judgment, are considered suitable to join the study.

Key Exclusion Criteria

• People who had COVID-19 in the past 3 months (90 days) before their first visit.
• People who got a COVID-19 vaccine, either as part of a research study or an approved vaccine, in the last 3 months-or plans to get one during the study.