Efficacy of a Plant-derived Quadrivalent Virus-like Particle (VLP) Vaccine in the Elderly

Inclusion Criteria

• Participants must have read, understood, and signed the informed consent form (ICF) prior to participating in the study; participants must also complete study-related procedures and communicate with the study staff at visits and by phone during the study;
• Participants must have a body mass index (BMI) ≤35 kg/m^2;
• Participants are considered by the Investigator to be reliable and likely to cooperate with the assessment procedures and be available for the duration of the study;
• Male and female participants must be 65 years of age and older at the Screening/Vaccination visit (Visit 1);
• Participants must be non-institutionalized (e.g. not living in rehabilitation centres or old-age homes; living in an elderly community is acceptable) and have 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 Principal Investigator or sub-Investigator (thereafter referred as Investigator) and determined by medical history, physical examination, and vital signs;

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

Exclusion Criteria

• According to the Investigator's opinion, history of an ongoing acute or evolving medical or neuropsychiatric illness. 'Evolving' was defined as:
• Requiring a new medical or surgical treatment during the three months prior to study vaccine administration unless the criteria outlined in inclusion criterion no. 5 can be met (i.e. the Investigator can justify inclusion based upon the innocuous nature of medical/surgical events and/or treatments);
• Requiring any significant change in a chronic medication (i.e. drug, dose, frequency) during the three months prior to study vaccine administration due to uncontrolled symptoms or drug toxicity unless the innocuous nature of the medication change meets the criteria outlined in inclusion criterion no. 5 and is appropriately justified by the Investigator.
• Any medical or neuropsychiatric condition or any history of excessive alcohol use or drug abuse that would render the participant unable to provide informed consent or unable to provide valid safety observations and reporting, including methadone (methadone as treatment for opioid dependence may be acceptable if the participant has been otherwise opioid-free for at least three years);
• Any autoimmune disease other than hypothyroidism on stable replacement therapy (including, but not limited to rheumatoid arthritis, systemic lupus erythematosus, Crohn's disease, type 1 diabetes, and inflammatory bowel disease) or any confirmed or suspected immunosuppressive condition or immunodeficiency including known or suspected human immunodeficiency virus (HIV), Hepatitis B or C infection, the presence of lymphoproliferative disease;
• Any history of status asthmaticus or ongoing serious problems with asthma, hospitalization for asthma control, or recurrent asthma episodes requiring medical attention in the last three years (one or more episodes per year);
• Administration or planned administration of any non-influenza vaccine within 30 days prior to randomization up to blood sampling on Day 21. Immunization on an emergency basis was evaluated case-by-case by the Investigator;
• Administration of any adjuvanted or investigational influenza vaccine within one year prior to randomization or planned administration prior to the completion of the study;
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