According to the Centers for Disease Control and Prevention (CDC), dengue is the fastest growing mosquito-borne disease in the world today, causing nearly 400 million infections every year. In the last 50 years dengue has spread from being present in a handful of countries to being endemic in 128 countries, where about 4 billion people live, and dengue incidence has likewise increased 30-fold in this time period. In addition, millions of travelers to those areas are also at risk of being bitten by the disease carrying mosquitoes.
Dengue has important economic consequences because of the burden to hospitals, work absenteeism and risk of death of symptomatic cases. Vector control has been the primary method of disease control. Despite such efforts, the number of cases remains high. Dengue affects people from all ages and socio-economic backgrounds, the greatest number of dengue cases worldwide occurs in the highly mobile and social segment of endemic populations that include pre-adolescents to adult ages of 9 years and above.
Transmitted by the main vector, the Aedes aegypti mosquito, there are 4 distinct, but closely related serotypes (DEN-1, DEN-2, DEN-3, Den-4) that cause dengue. Recovery from infection by 1 serotype has been known to provide lifelong immunity against that particular serotype. However, cross-immunity to the other serotypes after recovery is only partial and temporary and subsequent infections by other serotypes increase the risk of developing severe and fatal dengue. Today (in countries where the vaccine is approved), mosquito control strategies such as habitat reduction and spraying insecticide can now be supplemented by vaccination.
Dengvaxia®, a live attenuated tetravalent chimeric vaccine, is the first vaccine licensed for the prevention of dengue in the world. Sanofi Pasteur's vaccine is a product of over two decades of scientific innovation as well as 25 clinical studies in 15 countries around the world. Approved in Mexico (December 9, 2015) and the Philippines (December 22, 2015) and regulatory approvals are expected in other countries where dengue is a public health priority. Other dengue vaccines (Takeda, NIAID and Butantan, GSK and WRAIR, Merck, NMRC) are also in the pipeline.
In the first reports from the trials, vaccine efficacy was 56.5% in the Asian study and 64.7% in the Latin American study in patients who received at least one injection of the vaccine. Efficacy varied by serotype. In both trials vaccine reduced by about 80% the number of severe dengue cases. Pooled efficacy and integrated safety analyses from the 25-month Phase III efficacy studies and the ongoing long-term studies, respectively, published in The New England Journal of Medicine (July 2015) affirmed the vaccine's consistent efficacy and longer-term safety profile in study population 9-16 years of age. In the pooled efficacy analysis in this age group, Dengvaxia® was shown to reduce dengue due to all four serotypes in two-thirds of the participants and prevent 8 out of 10 hospitalizations and up to 93% of severe dengue cases.