This prospective, randomized, double-blind, placebo-controlled release study will enroll approximately 300 healthy adults 18 to 49 years of age. Eligible subjects will be randomly assigned in a 4:1 fashion to receive a single dose of trivalent vaccine or placebo by intranasal spray. Randomization will be stratified by site. This study will be conducted at 3 sites in the United States of America. Each subject will receive 1 dose of investigational product on Day 1. The duration of study participation for each subject is the time from study vaccination through 180 days after study vaccination.
