Dengue Serostatus and Dengue Vaccine Safety and Efficacy

To the Editor: Post hoc analysis of Sanofi’s Dengvaxia (CYD-TDV) vaccine by Sridhar et al. (July 26 issue)¹ provides evidence for an increased risk of severe dengue virus (DENV) disease among DENV-seronegative vaccinees. The authors address the possibility of antibody-dependent enhancement, but T-cell–mediated immunopathology represents another plausible explanation for this clinical outcome. Vaccine efficacy among young children is lost within 3 to 4 years after Dengvaxia immunization.² If levels of protective antibodies decline and DENV envelope-specific T-cell memory remains intact, then a proportion of persons may become susceptible to infection in the presence of an overly robust T-cell response; this . . .