Since World War II, the dengue viruses have achieved pandemic status, spreading throughout more than a hundred tropical and subtropical countries. Every year, dengue viruses infected tens of millions, causing about 500,000 hospitalizations and thousands of deaths. To date, no vaccine has been developed that has shown promise in protecting against dengue virus infections — until now.
On January 8, 2015, Luis Villar and colleagues published the results of a newly developed dengue virus vaccine that includes all four dengue virus serotypes (Villar L, et al. Efficacy of a Tetravalent Dengue Vaccine in Children in Latin America. N Engl J Med. 2015 Jan 8;372(2):113-23). Scientists made this vaccine by taking yellow fever vaccine (17D strain) and replacing two yellow fever genes (the envelope gene and the pre-membrane gene) with the envelope and pre-membrane genes from each of the four serotypes of dengue virus. (Dengue and yellow fever viruses are from the same virus family: Flaviviruses.)
A total of 20,869 healthy children from five Latin American countries received either the four-valent dengue vaccine or placebo at 0, 6, and 12 months. Children were then followed for 25 months and primary outcome was determined by protection against symptomatic, virologically-confirmed dengue virus. Researchers found that protective efficacy against all dengue disease was 64.7 percent (50 percent for type 1; 42.3 percent for type 2; 74 percent for type 3; and 77.7 percent for type 4). More importantly, protective efficacy against severe disease was 95.5 percent. The safety profile for the vaccine was similar to that for placebo.
This is the first large, prospectively controlled study to show a high level of efficacy against dengue infection and promises for a brighter future for those children who live in regions where dengue virus infections are common.