Healthy adult subjects will be screened with the objective to randomize 96 subjects with the lowest levels of H3 hemagglutination inhibition (HAI) titers that meet all inclusion/exclusion criteria and have signed an informed consent. Subjects will be rank-ordered from low to high based on their HAI titer. Subjects will then be assigned treatment based on a randomization to either active vaccine or placebo. The first two subjects dosed in each dose cohort will serve as sentinels and will receive active IP (not randomized).
Subjects will receive a single dose inoculation of the H3N2 M2SR seasonal monovalent influenza vaccine administered intranasally as a liquid formulation, or placebo (saline). The sentinel subjects will be vaccinated in dose cohort 1 and a safety monitoring committee (SMC) will conduct a review of safety data, tolerability, reactogenicity, and clearance of infectious virus prior to dosing the remaining subjects of the cohort with active or placebo.
After the last subject in the cohort has been followed for at least 7 days the SMC will conduct another review of safety data prior to proceeding to the next higher dose level: Cohort 2. The same processes of sentinel subject dosing and SMC review will be conducted for Cohorts 2 and 3.