This study is testing a new type of vaccine for the flu, called an mRNA vaccine, which uses a small piece of genetic material to help the body produce a defense against the virus. The focus is on a flu strain called H5. The study will see if the vaccine is safe and how well it works in both younger and older adults. Each participant will be involved for about 13 months and receive two injections 21 days apart. The study includes 7 visits to the clinic and one call.

To be part of the study, you must be 18 or older and, if you're a woman, not pregnant. You shouldn't have any major health issues like immune system problems or certain past vaccine reactions.

• The study lasts for about 13 months.
• Participants will have 2 injections and 7 visits to monitor their health.
• It's important to be healthy and not pregnant to join.