This study will evaluate the immune response produced by a seasonal LAIV. The initial vaccination will be followed 2 months later by an open-label inpatient trial evaluating the subsequent response (safety, infectivity, clinical response, and viral shedding) following administration of the wild-type A/California/2009-like influenza challenge virus.~Healthy adult participants will be randomized into two groups. On Day 0, Group 1 will receive a single dose of an intranasal LAIV. Group 2 will receive a single dose of intranasal placebo. Study visits will occur on Days 0, 3, 7, 14, and 28.~On Day 54, participants will be admitted to the isolation unit for the inpatient portion of the study, and both groups will receive an intranasal dose of wild-type A/California/2009-like influenza challenge virus on Day 56. On Day 65, participants who are no longer shedding virus will be discharged.~Follow-up study visits will occur after discharge from the isolation unit on Days 70, 84, 112, and 180. Study visits during either the inpatient or outpatient portions of the trial may include physical examinations, collection of blood and urine samples, electrocardiogram (ECG), nasal washes and swabs, and nasal mucus weighing.
The purpose of this study is to evaluate the immune response produced by a seasonal live attenuated influenza vaccine (LAIV) when compared to placebo. The initial vaccination will be followed 2 months later by an inpatient trial evaluating safety, infectivity, clinical response, and viral shedding after exposure to the wild-type A/California/2009-like influenza challenge virus.