Study to Assess the Safety and Immunogenicity of Monovalent mRNA NA Vaccine in Adult Participants 18 Years of Age and Older

This study will include a screening visit, 6 study visits occurring on Days 1, 3, 9, 29, 91, and 181, and a safety follow-up telephone call on Day 366.

Inclusion criteria

• Aged 18 years or older 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 study intervention administration until at least 12 weeks after study intervention administration
• A female participant of childbearing potential must have a negative highly sensitive pregnancy test (urine or serum as required by local regulation) within 8 hours before administration of study intervention.
• Informed consent form has been signed and dated.

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 systemic hypersensitivity to any of the study intervention components; history of a life-threatening reaction to the study interventions used in the study or to a product containing any of the same substances
• Moderate or severe acute illness/infection (according to investigator judgement) or febrile illness (temperature ≥100.4°F) on the day of study intervention administration.
• Have known or recently active (12 months) neoplastic disease or a history of any hematologic malignancy.
• Have any diagnosis, current or past, of autoimmune disease.
• Body mass index of 40 kg/m2 or higher.
• Receipt of immune globulins, blood, or blood-derived products in the past 3 months.
• Have taken high-dose inhaled corticosteroid (≥500 μg of fluticasone) within 6 months prior to study vaccination.
• Self-reported or documented seropositivity for HIV, hepatitis B virus, or hepatitis C virus.