The results of advanced trials for a promising vaccine have bolstered hopes that it could one day protect residents from a crippling and widespread disease.
Dengue hemorrhagic fever can last a week or more. Because it's caused by a virus, treatment options are limited. Bed rest and pain killers are normally prescribed for the lethargy, headaches, nose and gum bleeds, bloody vomiting, and other symptoms that accompany the fever.
Hundreds of millions of people are infected by a Dengue virus every year, and more than a third of the world's population lives in areas where residents are at risk of catching the virus from a mosquito. Scientists warn that climate change could help Dengue fever cement a foothold in the United States, with warmer and wetter weather expanding the ranges of Dengue-spreading species of mosquitoes. In 2009 and 2010, 28 people in Florida were struck with the disease—the first such outbreak in the Sunshine State in four decades.
"[T]his trial was successfully done over more than 2 years in diverse dengue-endemic areas in Asia, a region that accounts for 70% of the global dengue burden."
So finding a way of providing protection against the disease has long been a high priority among medical researchers.
The results of earlier trials involving about 4,000 healthy Thai schoolchildren suggested that the so-called CYD-TDV vaccine was safe for the kids who were injected with it. But they also suggested that it could be relatively safe for the virus. The vaccine reduced Dengue infections by about a third compared to those that took placebos. "These data show for the first time that a safe vaccine against dengue is possible," the researchers concluded in their paper, which was published in The Lancet in 2012.
As that paper was being proofed and finalized, researchers were already studying the effects of different strains of the vaccine in thousands of children in five Asia-Pacific countries. The study results, published online Friday by The Lancet, were more encouraging. Rates of infection with two Dengue strains were reduced by three quarters. Infections by a strain that were more prevalent among the Thai children were reduced by just a third.
"[T]his trial was successfully done over more than 2 years in diverse dengue-endemic areas in Asia, a region that accounts for 70% of the global dengue burden," the researchers wrote in the paper. "In this setting, we recorded promising results pointing to a substantial effect on severe disease manifestations."
Annelies Wilder-Smith, the scientific coordinator of DengueTools, studied the results and wrote in a commentary for The Lancet that they "may signify the dawn of a new era in dengue control." But she noted that "the morning fog has not yet lifted as dengue continues to puzzle."
"That efficacy in younger age groups was far lower than that in older children is a finding which is of concern," Wilder-Smith wrote. "Of greater concern is the relative lack of vaccine efficacy in participants who were dengue-virus naive. ... Therefore, the CYD-TDV vaccine might be of limited use in countries with low dengue endemicity, or in international travellers from non-dengue-endemic countries."