Late last year, the developer of the world’s first and so far only dengue vaccine warned that people who had no prior exposure to the mosquito-transmitted virus before being vaccinated were at heightened risk of severe disease should they subsequently be infected by a different dengue strain.
The warning from Sanofi Pasteur — and the World Health Organization recommendation that only those with prior exposure be vaccinated — was based on a new analysis of data from three clinical trials that led to the vaccine’s licensure in late 2015. Biostatisticians from Fred Hutchinson Cancer Research Center contributed new statistical methods as part of this new analysis, which was published last week in the New England Journal of Medicine.
The most common mosquito-borne disease in the Americas, dengue flourishes in tropical and subtropical countries. Any one of four closely related dengue viruses can cause a flu-like illness as well as severe dengue disease that is potentially lethal. Those at highest risk of developing severe disease are people who are infected a second time by a different dengue virus strain. In those not previously exposed, one hypothesis is that the vaccine may have had a similar effect as a first infection, raising the risk that a later infection would be severe and more likely to require hospitalization.