Study on an Investigational Yellow Fever Vaccine Compared With YF-VAX in Adults in the USA

Inclusion Criteria: * Aged 18 years to 60 years on the day of inclusion. * A female participant is eligible to participate if she is not pregnant or breastfeeding and one of the following conditions applies: Is of non-childbearing potential. To be considered of non-childbearing potential, a female must be postmenopausal for at least 1 year, or surgically sterile. OR Is of childbearing potential and agrees to use an effective contraceptive method or abstinence from at least 4 weeks prior to vaccination until at least 4 weeks after vaccination. A participant of childbearing potential must have a negative highly sensitive pregnancy test (urine or serum as required by local regulation) before any dose of study intervention on Day 1 and will be repeated on Day 29 to confirm the participant is still not pregnant within the 28 days of vaccine administration. * Informed consent form has been signed and dated. * Able to attend all scheduled visits and to comply with all study procedures. Exclusion Criteria: * Known or suspected congenital or acquired immunodeficiency; or receipt of immunosuppressive therapy, such as anti-cancer chemotherapy, or radiation therapy, within the preceding 6 months; or long-term systemic corticosteroid therapy (prednisone or equivalent for more than 2 consecutive weeks within the past 3 months). * Known history of flavivirus infection. * Known systemic hypersensitivity to any of the vaccine components, eggs, or history of a life-threatening reaction t…