A prospective, randomized, blinded Phase 4 clinical trial that will be conducted during the 2017/2018 and 2018/2019 influenza seasons.

During each season, approximately 220 older adults will be enrolled at Duke University Medical Center and 140 older adults at Boston University Medical Center. Eligible subjects will be randomized to receive either adjuvanted influenza vaccine or High-Dose influenza vaccine. All subjects will receive a vaccine and provide a blood draw at Visit 1, and then return for a second blood draw without vaccination about 4 weeks later to assess for influenza antibody titers.

A subset of 100 subjects at Duke will provide a third blood draw 6 months post-vaccination to assess for the waning of influenza antibody titers. Subjects will record the occurrence of local and systemic reactions (including fever, pain, tenderness, swelling, redness, general systemic systems), unsolicited adverse events, medical care utilization, and changes in medications over 8 days following vaccination.

In addition, serious adverse events and events of clinical interest will be assessed through 42 days post-vaccination. Health-related quality of life will be assessed pre-vaccination (Day 1) and on Days 3 and 9 post-vaccination.