This study compares the new flu vaccine mRNA-1010 with a vaccine already in use for people aged 50 and older. mRNA-1010 is a new type of flu shot that helps the body fight off flu viruses. The study checks how safe it is and if it works well compared to the current vaccine. It focuses on people who might get the flu caused by flu viruses A or B, confirmed by a special test called RT-PCR (reverse transcription polymerase chain reaction), which finds the virus in your body.

Key Points:

• Participants need to be 50 years or older and follow specific health guidelines.
• The study will require multiple visits and testing over a specified period.
• Participants must follow certain health rules, like not taking other vaccines or flu treatments before and during the study.

Before joining, you need to be healthy, not have certain health issues, and agree to follow the study's rules. Women who can get pregnant must use birth control. If you recently had flu or other vaccines, you might not qualify. The study aims to find out if the new vaccine is a good option for fighting the flu.