A Study of mRNA-1010 Seasonal Influenza Vaccine in Adults

A Phase 3, Randomized, Stratified, Observer-blind, Active-Controlled Study to Evaluate the Immunogenicity and Safety of mRNA-1010 Seasonal Influenza Vaccine in Adults 18 Years and Older

The primary objectives of this study are to evaluate the humoral immunogenicity of mRNA-1010 relative to that of an active comparator against vaccine-matched influenza A and B strains at Day 29, and to evaluate the safety and reactogenicity of mRNA-1010.

Inclusion Criteria:

• Investigator has assessed that the participant understands and is willing and physically able to comply with protocol mandated follow-up, including all procedures.
• For female participants of childbearing potential: negative pregnancy test, adequate contraception or has abstained from all activities that could result in pregnancy for at least 28 days prior to Day 1, and agreement to continue adequate contraception through 90 days following vaccine administration.

Exclusion Criteria:

• Participant has had close contact to someone with SARS-CoV-2 infection or COVID-19 as defined by the United States (US) CDC or has had a positive SARS-CoV-2 test in the past 10 days prior to the Screening Visit.
• Participant is acutely ill or febrile (temperature ≥38.0℃ [100.4°F]) 72 hours prior to or at the Screening Visit or Day 1. Participants meeting this criterion may be rescheduled within the 28-day screening window and will retain their initially assigned participant number.
• Participant has a history of a diagnosis or condition that, in the judgment of the investigator, is clinically unstable or may affect participant safety, assessment of safety endpoints, assessment of immune response, or adherence to study procedures.
• Reported history of anaphylaxis or severe hypersensitivity reaction after receipt of any mRNA or influenza vaccines or any components of the mRNA or influenza vaccines, including egg protein.
• Participant has received systemic immunosuppressants or immune-modifying drugs for >14 days in total within 180 days prior to the Screening Visit (for corticosteroids, ≥10 milligrams (mg)/day of prednisone or equivalent) or is anticipating the need for systemic immunosuppressive treatment at any time during participation in the study. Inhaled, nasal, and topical steroids are allowed.
• Participant has received any vaccine authorized or approved by local health agency ≤28 days prior to study injection (Day 1) or plans to receive a vaccine authorized or approved by local health agency within 28 days before or after the study injection.
• Participant is not aware whether they have received an influenza vaccine in the past 12 months or has received a seasonal influenza vaccine or any other investigational influenza vaccine within 180 days prior to Day 1.
• Participant has tested positive for influenza by local health authority-approved testing methods within 180 days prior to the Screening Visit.
• Participant has donated ≥450 milliliters (mL) of blood products within 28 days prior to the Screening Visit or plans to donate blood products during the study.

Note: Other inclusion and exclusion criteria may apply.