How close are we to beating dengue?

This article is published in collaboration with The Bill and Melinda Gates Foundation.

According to the World Health Organization (WHO), 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 mosquitos.

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 preadolescents to adult ages of 9 years and above.

Transmitted by the main vector, the Aedes aegypti mosquito, there are 4 distinct, but closely related, viruses 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.

References:

Capeding M.R. et.al, Clinical efficacy and safety of a novel tetravalent dengue vaccine in healthy children in Asia: a phase 3, randomised, observer-masked, placebo-controlled trial ; Volume 384, Issue 9951, 11-17 October 2014, Pages 1358-1365.

Hadinegoro, Sri Rezeki S., et al. Efficacy and Long-Term Safety of a Dengue Vaccine in Regions of Endemic Disease Integrated Analysis of Efficacy and Interim Long-Term Safety Data for a Dengue Vaccine in Endemic Regions. July 27, 2015DOI: 10.1056/NEJMoa1506223.

Joseph R. Egger, Paul G. Coleman. Age and Clinical Dengue Illness. Emerg Infect Dis. 2007 June; 13(6): 924-927.San Martin JL, Brathwaite O, Zambrano B, et al. The epidemiology of dengue in the americas over the last three decades: a worrisome reality. Am J Trop Med Hyg 2010;82:128-35.

Shepard DS, Halasa YA, Undurraga EA, Stanaway J. Global economic cost of dengue illness. Poster presented at: American Society of Tropical Medicine and Hygiene Annual Meeting; Oct. 25-29, 2015, Philadelphia, PA, Poster 781.

Schwartz LM, Halloran ME, Durbin AP, Longini IM Jr, et al. The dengue vaccine pipeline: Implications for the future of dengue control. Vaccine 33 (2015) 3293–3298.

Villar L, Dayan GH, Arredondo-Garcia JL, Rivera DM, Cunha R, Deseda C et al. Efficacy of a tetravalent dengue vaccine in children in Latin America. N Engl J Med. 2015.

WHO. Dengue and severe dengue. Fact Sheet N° 117. May 2015. http://www.who.int/topics/dengue/en

Publication does not imply endorsement of views by the World Economic Forum.

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Author: Melvin Sanicas is Global Health Fellow and Program Officer, Global Health, Bill and Melinda Gates Foundation.

Image: A woman sleeps under a mosquito net with her two-year-old son, who is suffering from dengue fever, inside a dengue ward of a local hospital in Rawalpindi, Pakistan, October 22, 2015. According to local media, thousands of patients suffering from dengue, a mosquito-borne disease, registered in various hospitals in Punjab and Sindh province. Pakistan suffered its one of its worst dengue outbreaks in 2011, when over 300 people died of the mosquito-borne disease. REUTERS/Faisal Mahmoud.