A Study to Evaluate the Efficacy of MEDI7510 in Older Adults

This study will be the first assessment of the efficacy of MEDI7510 for the prevention of respiratory syncytial virus (RSV) disease. It will also provide estimates of vaccine efficacy and of endpoint incidence in the placebo arm. It will also assess the safety and immunogenicity of concurrent dosing of MEDI7510 and IIV to expand on the observations made in the Phase 1b study of MEDI7510. It will also expand the safety database of participants dosed with MEDI7510. The study will also assess the immune response to MEDI7510 in Season 1 and Season 2.

A Phase 2b, double-blind, randomized, and controlled study to evaluate the efficacy of MEDI7510 in approximately 1,900 adult participants, globally, 60 years or older. Participants will be randomized in a 1:1 ratio to receive a single intramuscular dose of each of 2 study vaccines in contralateral arms: MEDI7510 + IIV or placebo + IIV in Season 1.

Participants who receive MEDI7510 in the Northern Hemisphere will be re-randomized and blinded in Season 2 to receive either MEDI7510 + IIV or placebo + IIV in a 1:1 ratio. Clinical efficacy will not be assessed in Season 2; however the safety of revaccination will be assessed in Season 2.

Eligibility Criteria:
Inclusion Criteria:

* Age ≥ 60 years at the time of screening.
* Medically stable such that, according to the judgment of the investigator, hospitalization within the study period is not anticipated and the subject appears likely to be able to remain in follow-up through the end of protocol-specified follow-up.
* (Season 2): Subject received MEDI7510 and IIV in the Northern Hemisphere in Season 1.

Exclusion Criteria:

* History of allergy to any component of the vaccine.
* Receipt of seasonal influenza vaccine within 6 months prior to Season 1 dosing.
* History of allergy to or intolerance of IIV.
* Pregnancy or potential to become pregnant during the study. Females who (1) have had a menstrual period within the 12 months prior to study enrollment or (2) are undergoing any fertility treatment or who plan to undergo fertility treatments during the study period are excluded.
* History of Guillain-Barré syndrome.
* Previous vaccination against RSV.
* History of allergy to eggs in adulthood.
* History of or current autoimmune disorder, with the exception of stable, treated hypothyroidism caused by autoimmune thyroiditis, which is acceptable.
* Immunosuppression caused by disease, including human immunodeficiency virus infection (assessed by history), or medications. Any receipt of oral or intravenous glucocorticoid therapy within 30 days prior to enrollment or planned dosing within the follow-up period would disqualify. Topical, intranasal, inhaled, or intra-articular corticosteroids do not disqualify. Expected need for immunosuppressive medications during the follow-up period would disqualify.
* History of cancer within preceding 5 years other than treated non-melanoma skin cancer, locally-treated cervical cancer or in situ carcinoma of the breast.
* Receipt of any non-study vaccine within 28 days prior to study dosing or expected receipt of non-study vaccine prior to the Day 29 visit in Season 1.
* Receipt of any investigational product (IP) in the 90 days prior to randomization or expected receipt of IP during the period of study follow-up.
* Receipt of immunoglobulins or blood products within 4 months of study dosing (120 days) or expected receipt of immunoglobulins or blood products during the period of study follow-up.
* Current bleeding or clotting disorder including use of anticoagulants other than drugs with anti-platelet activity (such as nonsteroidal anti-inflammatory drugs, clopidogrel, ticagrelor or aspirin).
* History of alcohol or drug abuse or psychiatric disorder that, in the opinion of the investigator, would affect the subject's safety or compliance with study.
* (Season 2): Related Grade 3 or 4 adverse event (AE) including Grade 3 or 4 local reaction to either MEDI7510 or IIV, any adverse event of special interest (AESI) for an adjuvanted vaccine, or any related serious adverse event (SAE).