Titled, “New chapter unfolding in the fight against dengue with an unwritten ending,” the Dengue Vaccine Initiative’s (DVI) editorial just published in the October issue of Transactions of the Royal Society of Tropical Medicine and Hygiene discusses the results of Sanofi’s dengue vaccine candidate Phase 3 trial in Asia. DVI experts explain that while these results show promising indications that a safe dengue vaccine is technically feasible, key questions remain that need to be addressed.

“Dengue is the most common and fastest growing mosquito-borne viral disease. […] The good news is, a vaccine is forthcoming. While this represents a new chapter in the fight against dengue, as it brings hope for a more sustainable strategy to prevent and control this disease, the ending is yet to be written.”

This new chapter has not come quickly. After over 60 years of research, the development of a dengue vaccine has accelerated dramatically only in recent years. Today, clinical trials are underway on at least five dengue vaccine candidates, and, as announced this year, a Phase 3 trial was successfully completed, for the very first time, on one of these candidates.  
This Phase 3 trial evaluated the efficacy and safety of Sanofi’s tetravalent dengue vaccine candidate in 10,275 children and teenagers in five countries in Asia. It showed efficacy of 57 percent against any virologically confirmed dengue. Vaccine efficacy was statistically significant for all serotypes except serotype 2, and the vaccine’s safety was reassuring. The trial results also provided new insights in exploratory analyses, showing an increase in vaccine efficacy with age and a reduction of risk of severe disease in vaccinated children.
DVI experts state that these findings put a vaccine firmly onto the agenda for dengue control. But, there are still several unknowns, showing the limited understanding of the immunology of dengue and challenges in measuring immune responses. For this reason, we need to ask more questions and invite further analysis, to help us write an ending for this chapter.