Phase II Trial to Evaluate Safety and Immunogenicity of a Dengue 1,2,3,4 (Attenuated) Vaccine

This is a phase II step-wise, randomized, multicenter, double-blind and controlled clinical trial to evaluate the safety and immunogenicity of a attenuated tetravalent lyophilized dengue vaccine manufactured by Butantan Institute. Three Clinical Sites at University of Sao Paulo - Brazil will participate in the study. A total of 300 volunteers will be recruited and divided into two steps: Step A (with no previous exposure to dengue) and Step B (with and without previous exposure to dengue). In step A the participants will be assigned to receive either the lyophilized vaccine, or the liquid vaccine(developed at NIH and produced and formulated at Butantan according to the NIH-Protocol), or the placebo. In Step B participants will be assigned to receive either the lyophilized vaccine, or the placebo. Both vaccine formulations (lyophilized and liquid) are composed of the same attenuated viruses: rDEN1∆30, rDEN2/4∆30(ME), rDEN3∆30/31, and rDEN4∆30. At the end of the study, 20 volunteers will have received the liquid formulation (NIH), 210 the lyophilized formulation (Butantan), and 70 will have received the placebo. All participants included in both steps will be followed by a period of five years after their inclusion in the study. The study hypothesis is that the investigational lyophilized dengue vaccine manufactured by Butantan Institute is safe and confers balanced immune response, after one dose of 1000PFU, to all for vaccine viruses.