A Phase 2b, double-blind, randomized, controlled study to evaluate the efficacy of MEDI7510 in approximately 1,900 adult subjects, globally, 60 years or older. Subjects 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.