Phase III Trial to Evaluate Efficacy and Safety of a Tetravalent Dengue Vaccine

This is a randomized, multicenter, double-blind, placebo-controlled Phase III study that will evaluate efficacy and safety of a live attenuated, tetravalent, lyophilized dengue vaccine produced by Butantan Institute. The study will be carried out in multiple sites in Brazil. The study will be community-based in select urban areas where there's dengue transmission. Study's intervention will be a single dose of the tetravalent dengue vaccine or placebo in a ratio 2:1. For efficacy analysis will be considered all dengue cases occurring after 28 days post-vaccination in the entire population of 16944 participants. For safety analysis participants will be divided in three age groups: 18 to 59 ys, 7-17 ys and 2 to 6 ys. In each of these age groups there will be a minimum of 4992 participants. The age groups of 18 to 59 ys and 7 to 17 ys will start first. Once safety data for the first 21 days after vaccination is analysed for 450 participants in 7-to17-ys age group, the following group, of 2 to 6 ys, will start. The study's hypothesis is that the vaccine under investigation and produced by Butantan Institute is safe and provides protection against dengue symptomatic disease of 80% or more with a lower bound of the 95% confidence interval of 25%. This way, the expected number of dengue cases virologically confirmed is 24 or more which will provide a response in terms of vaccine efficacy. All participants will be followed up for five years to verify dengue incidence, regardless severity.