Adjuvanted Seasonal Recombinant Quadrivalent Virus-Like Particles (QVLP) Influenza Vaccine in Adults 65 Years of Age and Older

Inclusion Criteria

• Participants read, understood, and signed the informed consent form prior to participating in the study; participants also completed study-related procedures and communicated with the study staff at visits and by phone during the study;
• Male and female participants 65 years of age and older at the Vaccination visit (Visit 2);
• Participants had a body mass index (BMI) < 30 kg/m2 at the Vaccination visit (Visit 2);
• Participants were considered by the Investigator to be reliable and likely to cooperate with the assessment procedures and be available for the duration of the study;
• Participants were non-institutionalized (e.g. not living in rehabilitation centers or old-age homes; living in an elderly community was acceptable) and had no acute or evolving medical problems prior to study participation and no clinically relevant abnormalities that could jeopardize participant safety or interfere with study assessments, as assessed by the Investigator and determined by medical history, physical examination, serology, clinical chemistry and hematology tests, urinalysis, and vital signs. Investigator discretion was permitted with this inclusion criterion;

Note: Participants with a pre-existing chronic disease were allowed to participate if the disease was stable and, according to the Investigator's judgment, the condition was unlikely to confound the results of the study or pose additional risk to the participant by participating in the study. Stable disease was generally defined as no new onset or exacerbation of pre-existing chronic disease 3 months prior to vaccination. Based on the Investigator's judgment, participants with more recent stabilization of a disease were also eligible.

Exclusion Criteria

• According to the Investigator's opinion, significant acute or chronic, uncontrolled medical or neuropsychiatric illness. Acute disease was defined as presence of any moderate or severe acute illness with or without a fever within 48 hours prior to the Vaccination visit (Visit 2). "Uncontrolled" was defined as:
• Requiring a new medical or surgical treatment during the 3 months prior to study vaccine administration;
• Required any significant change in a chronic medication (i.e. drug, dose, frequency) during the 3 months prior to study vaccine administration due to uncontrolled symptoms or drug toxicity unless the innocuous nature of the medication change met the criteria outlined in inclusion criterion #5 and was appropriately justified and documented by the Investigator. Note: Investigator discretion was permitted with this exclusion criterion.
• Any confirmed or suspected current immunosuppressive condition or immunodeficiency, including cancer, human immunodeficiency virus, hepatitis B or C infection (participants with a history of cured hepatitis B or C infection without any signs of immunodeficiency at present time were allowed). Investigator discretion was permitted with this exclusion criterion;
• Current autoimmune disease requiring systemic treatment (such as rheumatoid arthritis, systemic lupus erythematosus, or multiple sclerosis). Investigator discretion was permitted with this exclusion criterion, and participants were eligible to participate with appropriate written justification in the source document (i.e. participants with a history of autoimmune disease who were disease-free without treatment for 3 years or more, or on stable thyroid replacement therapy, mild psoriasis [i.e. a small number of minor plaques requiring no systemic treatment], etc.);
• Administration of any non-influenza vaccine within 30 days prior to the Vaccination visit (Visit 2); planned administration of any vaccine up to Day 28 of the study. Immunization on an emergency basis during the study was evaluated on case-by-case basis by the Investigator.

Note: Administration of an authorized COVID-19 vaccine prior to or during the study was acceptable;

• Administration of influenza vaccine within 6 months pr