This clinical trial focuses on testing a new influenza vaccine called mRNA-1010 in comparison with an already approved flu vaccine. The study aims to determine how safe and effective the new vaccine is in protecting adults aged 50 and older against the flu. The new vaccine uses messenger RNA technology, which is different from traditional flu vaccines.

During the study, participants will receive either the new mRNA-1010 vaccine or a standard licensed influenza vaccine called Influsplit Tetra through an intramuscular injection. Both vaccines are designed to protect against different strains of influenza viruses. The study will monitor participants for any side effects and track how well the vaccines prevent flu-like illness caused by influenza viruses.

The research team will collect information about vaccine reactions in the first week after vaccination, track any unexpected health issues for 28 days, and continue monitoring participants’ health for approximately 6 months. They will also measure how well the body’s immune system responds to the vaccines by checking blood samples and documenting any cases of flu-like illness that occur during the study period.