Pandemic flu H5 HA mRNA SD2 vaccine(Sanofi)

The purpose of this phase 1/2 study is to investigate the safety and immunogenicity of different doses (high, medium and low) of a second generation structurally designed (SD2) H5 messenger ribonucleic acid (mRNA) vaccine against pandemic H5 influenza virus (pandemic flu H5 hemagglutinin (HA) mRNA SD2) in healthy younger and older adults.
The study will aim to identify the appropriate dose for further clinical development of a potential pandemic response vaccine.
The study duration per participant will be approximately 13 months. There will be two injections of placebo or pandemic flu H5 mRNA vaccine 21 days apart at high, medium and low doses.
Study visits/contact include: 7 study visits and 1 telephone call. Vaccination visits (including blood samples) will occur at Day 01 and Day 22. Short-term follow-up visits (including blood samples) will occur 8 and 21 days after each injection. Participants will be also followed up (including blood samples) at 3 and 6 months after 2nd injection, and at 12 months after 2nd injection for safety.