Safety and Immunogenicity of a Recombinant Tetravalent Dengue Vaccine in 9-16 Year Olds A Randomized, Controlled, Phase II Trial in Latin America

Background: The dengue virus is a member of the Flavivirus (FV) genus, which also includes the yellow fever virus. Dengue disease is caused by any 1 of 4 dengue virus serotypes and is a serious public health concern in Latin America. This study evaluated the safety and immunogenicity of a candidate recombinant, live-attenuated, tetravalent dengue vaccine (CYD-TDV) in 9-16 year olds in Latin America. Methods: In this randomized, blinded, controlled study, volunteers received either 3 doses of CYD-TDV (n = 401) or placebo as first and second injection and tetanus/diphtheria/acellular pertussis vaccine as third injection (n = 199) at 0, 6 and 12 months. Adverse events were documented. Plaque reduction neutralization test antibody titers against the 4 CYD-TDV parental strains were measured before and 28 days after each dose. Seropositivity was defined as antibody titers 10 1/dil. Results: The number of adverse reactions decreased after each successive CYD-TDV dose. After each CYD-TDV dose, antibody titers against all 4 serotypes were higher than baseline and respective predose titers. After the third dose of CYD-TDV, 100%, 98.6% and 93.4% of participants were seropositive for at least 2, at least 3 or all 4 serotypes, respectively. Higher antibody titers were observed in participants in the CYD-TDV group who were FV-seropositive at baseline compared with those who were FV-seronegative. Conclusions: CYD-TDV had a favorable safety profile and elicited antibody responses against all 4 dengue virus serotypes in 9-16 year olds in Latin America. These findings support the continued development of CYD-TDV.