This study tests an H5N8 influenza (flu) vaccine made from eggs. It checks how safe the vaccine is and how well it works when given at three different doses—low, medium, or high. Some participants will get the vaccine with an adjuvant, a special substance that can help the vaccine work better. Participants in this study will be healthy adults aged 18 and older. They will receive two shots in the arm and be in the study for about 14 months. **Key Points**:

• Participants will get 2 vaccine shots over 14 months.
• The study includes only healthy adults, aged 18 and above.
• Participants must attend all visits and follow all instructions.

*Note:* Some people cannot join, such as those with certain health issues or those who have recently had other vaccines. Participants will be checked by doctors to ensure they are healthy enough to join. The study will help understand how well this new flu vaccine works and if it is safe.