Dengue vaccine increases the risk of severe dengue in unexposed children.
Effect of Dengue Serostatus on Dengue Vaccine Safety and Efficacy
S. Sridhar, A. Luedtke, E. Langevin, M. Zhu, et al. The New England Journal of Medicine, (2018), DOI: 10.1056/NEJMoa1800820.
In efficacy trials of a tetravalent dengue vaccine, study authors found: “…in the absence of previous dengue exposure, the (Sanofi) vaccine partially mimics primary infection and increases the risk of severe dengue.” (800,000 kids were already vaccinated before they pulled the vaccine.)