What is likely to be the first dengue vaccine on the market has shown encouraging results in a clinical trial in Latin America, cutting disease incidence in recipients by 60.8%, its developer announced yesterday. The vaccine could be approved for use as early as next year; then, dengue-affected countries would face a tough decision in weighing whether the limited protection it confers will be worth the vaccine’s cost.
Spread by mosquitoes, dengue is endemic throughout tropical and subtropical regions worldwide and is an especially heavy health care burden in Asia and the Americas. Because there are no drugs for dengue, each year an estimated 20,000 people die and another 500,000 require hospitalization. An initial infection with one of the four distinct dengue virus serotypes is typically mild. Infection with a second serotype often causes severe symptoms, which include a debilitating fever, joint and muscle aches, and internal bleeding. Dengue experts believed that to stave off complications of a second infection, a vaccine must provide balanced protection against all four serotypes—and that has proven difficult to achieve.
In an earlier trial in Southeast Asia, more than 10,000 children and young adults in five countries received three doses. In addition to reducing the overall incidence of dengue, the vaccine cut cases of severe disease by 88.5%. But the vaccine was only 35% effective against serotype 2. That was the most prevalent serotype in the region at the time, reducing overall efficacy.
In the Latin America study, involving 20,875 participants aged 9 to 16 in five countries, the vaccine reduced hospitalizations 80.3% and cut the incidence of dengue 2 by 42.3%. Scientists from pharmaceutical giant Sanofi Pasteur, the vaccine’s maker, will present details of the trial at the American Society of Tropical Medicine and Hygiene annual meeting in New Orleans in November.
Sanofi Pasteur has a $400 million facility in Neuville-sur-Saône, France, capable of producing 100 million doses of the vaccine per year. The company previously told Science it will likely start seeking approval to market the vaccine later this year or early in 2015. But some countries may be reluctant to embrace it. Based on the vaccine’s limited protection against dengue types 1 and 2 in the trial in Southeast Asia, Singapore’s environment minister Vivian Balakrishnan declared last month that it’s "not good enough" to be added to his country’s national immunization program.