Safety and Immunogenicity of a Single Dose of Intranasal Seasonal Trivalent Live-Attenuated Influenza Vaccine

In this Phase II randomized controlled clinical trial, generally healthy male and female children from 24 through 59 months of age will be enrolled in Kamalapur (Dhaka), Bangladesh. The study is expected to continue for at least 6 months following vaccination. The experimental intervention is Serum Institute of India Ltd\'s Trivalent, Seasonal Live Attenuated Influenza Vaccine (SIIL LAIV). The study vaccine has been formulated according to WHO recommendations for the 2011-2012 Northern Hemisphere influenza season. The SIIL LAIV is administered in a 0.5 ml intranasal dose (one spray of 0.25 ml per nostril) via a reusable sprayer device and a single-use nozzle that produces a fine mist that is primarily deposited in the nose and nasopharynx. The comparator vaccine will be an inactive placebo identical in appearance to the active vaccine. The primary study hypothesis is that LAIV is safe and well tolerated by children aged 24 through 59 months in Bangladesh. A secondary hypothesis is that LAIV is immunogenic among children receiving study vaccine as compared to children receiving placebo.