This was a prospective, randomized, double-blind, placebo-controlled release study. Eligible subjects were randomly assigned in a 4:1 fashion to receive a single dose of trivalent vaccine or placebo by intranasal spray. Randomization was stratified by site. Each subject received 1 dose of study vaccine on Study Day 0. The duration of study participation for each subject was the time from study vaccination through 180 days after study vaccination.