The purpose of this clinical trial is to learn about the safety and effects of the study vaccine for the potential prevention of influenza. The study vaccine is called Self-Amplifying Ribonucleic Acid vaccine (saRNA vaccine). This study is seeking participants who: * Are between the age of 18 to 49 years old. * Are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, lifestyle considerations, and other study procedures. * Are healthy as determined by medical history, physical examinations, and the study doctor. * For male participants, can father children and willing to use an acceptable method of contraception. Female participants who are not of childbearing potential; or male participant not able to father children. * Are capable of giving signed informed consent. Participants will receive either the saRNA vaccine, a licensed Influenza Vaccine (QIV) or a placebo. Participants will not know which vaccine they receive in advance. A placebo does not have any medicine in it but looks just like the study medicine. Participants will receive the study vaccines as a single shot in the arm. We will compare participant experiences to help us determine if the saRNA vaccine is safe and effective. Participants will take part in this study for 6 months. During this time, they will receive the study vaccine and participate in follow-up visits.
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Percentage of participants reporting local reactions
Timeframe: For 10 days after vaccination
Percentage of participants reporting systemic events
Timeframe: For 10 days after vaccination
Percentage of participants reporting adverse events
Timeframe: From vaccination to 4 weeks after vaccination
Percentage of participants reporting serious adverse events
Timeframe: From vaccination to 6 months after vaccination
Percentage of participants with abnormal hematology and chemistry laboratory values
Timeframe: 2 days after vaccination
Percentage of participants with abnormal hematology and chemistry laboratory values
Timeframe: 1 week after vaccination
Percentage of participants with grading shifts in hematology and chemistry laboratory assessments
Timeframe: Between baseline and 2 days after vaccination
Percentage of participants with grading shifts in hematology and chemistry laboratory assessments
Timeframe: Between baseline and 1 week after vaccination
Percentage of participants with new electrocardiogram (ECG) abnormalities
Timeframe: 2 days after vaccination
Percentage of participants with new ECG abnormalities
Timeframe: 1 week after vaccination