Safety and Immunogenicity of the Sing2016 M2SR H3N2 Monovalent Influenza Vaccine in Adults Ages 50 to 85 Years Old

This group will receive a dose of the Sing2016 M2SR H3N2 monovalent influenza vaccine administered intranasally on Day 1 followed by IIV at least 28 days later.

This group will receive saline placebo administered intranasally on Day 1 followed by IIV at least 28 days later.