A Study To Learn About The Study Vaccine (Called Self-Amplifying Ribonucleic Acid (RNA)) For The Prevention of Influenza

Inclusion Criteria: * Male or female participants 18 to 49 years of age. * Participants who are willing and able to comply with all scheduled visits, treatment plan, laboratory tests, lifestyle considerations, and other study procedures. * Healthy participants who are determined by medical history, physical examination (if required), and clinical judgment of the investigator to be eligible for inclusion in the study. * Male participant who is able to father children and willing to use an acceptable method of contraception; or female participant not of childbearing potential; or male participant not able to father children. * Capable of giving signed informed consent. Exclusion Criteria: * Other medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behavior or laboratory abnormality that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study. * History of severe adverse reaction associated with a vaccine and/or severe allergic reaction (eg, anaphylaxis) to any component of the study intervention. * Immunocompromised individuals with known or suspected immunodeficiency, as determined by history and/or laboratory/physical examination. * Bleeding diathesis or condition associated with prolonged bleeding that would, in the opinion of the investigator, contraindicate intramuscular injection. * Women who are pregnant or breastfeeding. * Allergy to egg proteins (egg or egg products) or chicken proteins. * Participant who has had significant exposure to laboratory-confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 infection), coronavirus disease 2019 (COVID-19), or influenza in the past 14 days known prior to Visit 1 * Any participant who has a SARS-CoV-2 RT-PCR or antigen test in the past 10 days prior to Visit 1 that has not been confirmed as negative. * Individuals who receive treatment with radiotherapy or immunosuppressive therapy, including cytotoxic agents or systemic corticosteroids, eg, for cancer or an autoimmune disease, or planned receipt throughout the study. * Receipt of blood/plasma products, immunoglobulin, or monoclonal antibodies, from 60 days before study intervention administration, or planned receipt throughout the study. * Vaccination with any influenza vaccine within 6 months (175 days) before study intervention administration. * Any participant who has received or plans to receive a nucleoside-modified messenger ribonucleic acid (modRNA)-platform SARS-CoV-2 vaccine within 60 days of Visit 1 * Previous vaccination with an saRNA or an alphavirus replicon vaccine preparation. * Participation in other studies involving study intervention within 28 days prior to study entry and/or during study participation. * Screening hematology/blood chemistry lab \>=Grade 1 abnormality. Except Bilirubin, other stable Grade1 abnormalities may be considered eligible by Investigator. * Screening electrocardiogram (ECG) that is consistent with probable or possible myocarditis or pericarditis, or demonstrates clinically relevant abnormalities that may affect participant safety or study results. * Investigator site staff or Pfizer employees directly involved in the conduct of the study, site staff otherwise supervised by the investigator, and their respective family members. * Participation in strenuous or endurance exercise through Visit 3. * Prior history of heart disease.