This Phase 3 study is a randomized, observer-blind study of MF59-adjuvanted influenza vaccine (aQIV or aTIV) compared with a non-adjuvanted influenza vaccine (QIV or TIV) in adults ≥65 years of age. The aim of the study is to evaluate MF59-adjuvanted influenza vaccine compared with non-adjuvanted influenza vaccine in the prevention of reverse transcription-polymerase chain reaction (RT-PCR)-confirmed influenza A and/or B in subjects ≥65 years of age.

Inclusion Criteria:

In order to participate in this study, all subjects must meet ALL of the inclusion criteria described.

1. Adults of ≥65 years of age on the day of vaccination.
2. Individuals who have voluntarily given written informed consent after the nature of the study has been explained according to local regulatory requirements, prior to study entry.
3. Individuals who have the ability to comply with study procedures including follow-up.

Exclusion Criteria:

In order to participate in this study, all subjects must not meet any of the exclusion criteria described below:

1. Bedridden subjects (i.e. confined to bed by sickness or old age).

2. Subjects that are incapacitated and because of that in need of a Legally Authorized Representative.

3. Receipt of any influenza vaccine within 6 months prior to enrollment or any plan to receive influenza vaccine while participating in the study.

4. Hypersensitivity, including allergy, to any component of vaccines whose use is foreseen in this study, or severe allergic reaction (e.g. anaphylaxis) to previous influenza vaccination.

5. Known history of Guillain-Barré syndrome or another demyelinating disease such as encephalomyelitis and transverse myelitis.

6. Clinical conditions representing a contra-indication to intramuscular administration of vaccines or blood draw.

7. Abnormal function of the immune system resulting from:

   1. Clinical conditions;
   2. Systemic administration of corticosteroids (PO/IV/IM) at a dose ≥20 mg/day of prednisone (or equivalent) for more than 14 consecutive days within 90 days prior to informed consent; Topical, inhaled and intranasal corticosteroids are permitted. Intermittent use (one dose in 30 days) of intra-articular corticosteroids are also permitted;
   3. Administration of antineoplastic and immunomodulating agents or radiotherapy within 90 days prior to informed consent.

8. Receipt of immunoglobulins or any blood products within 180 days prior to informed consent.

9. Receipt of any investigational or non-registered product (drug or vaccine) other than the study vaccine within 30 days preceding the study vaccination, or planned use during the entire study period.

10. Acute (severe) febrile illness.

11. Any other clinical condition that, in the opinion of the investigator, might interfere with the results of the study or pose additional risk to the subject due to participation in the study.

12. Study personnel or immediate family members (brother, sister, child, parent) or the spouse of study personnel.

Seqirus will consider on a case-by-case basis requests to share Individual Patient Data (IPD) with external bona-fide, qualified scientific and medical researchers. For information on the process and requirements for submitting a voluntary data sharing request for IPD, please contact Seqirus at seqirus.clinicaltrials@seqirus.com.

Requests for IPD will generally be considered once review by major regulatory authorities (ie FDA, EMA) is complete and the primary publication is available.

Proposed research should seek to answer a previously unanswered important medical or scientific question.

Applicable country specific privacy and other laws and regulations will be considered and may prevent sharing of IPD.

If the request is approved and the researcher has executed an appropriate data sharing agreement, IPD that has been appropriately anonymized will be available.