By Sandra Basu
WASHINGTON — A human clinical trial this year for a vaccine designed to protect against all four serotypes of the dengue virus is giving military researchers hope that they are closer to developing a vaccine against the debilitating disease.
Development of an effective vaccine is not only a benefit to the tens of millions of patients who suffer from the disease around the world, it also could assure troop readiness if the United States were to deploy in a region where dengue fever is common.
“We don’t know where we are going to be tomorrow. We can be required to go anywhere in the world, [which] is why we have to have a vaccine protecting troops,” Lt. Cmdr. Tad Kochel, head of the Naval Medical Research Center (NMRC) Viral and Rickettsial Diseases program in Silver Spring, MD,, told U.S. Medicine. He also is an expert on dengue and is the lead on the study.
Pursuit of a dengue vaccine is a joint Army-Navy program.
As many as 100 million people are infected yearly by dengue, frustrating public-health officials from around the world.
This vaccine candidate, the culmination of 19 years of work, is the first tetravalent dengue DNA vaccine to undergo human testing. Partnering with Vical, a San Diego-based biopharmaceutical research enterprise. NMRC researchers developed the tetravalent DNA vaccine formulated with Vical’s Vaxfectin adjuvant. The Phase 1 human clinical trial that began this year is evaluating the vaccine formulated with and without Vaxfectin.
“We partnered with Vical to use their adjuvant to enhance the immune response,” Capt. Kevin Porter, director of infectious diseases research at the Naval Medical Research Center, told U.S. Medicine.
The dengue virus is transmitted by mosquitoes. Although dengue is uncommon in the continental United States, it is endemic in Puerto Rico and in many locations in Latin America and Southeast Asia. In addition, periodic outbreaks occur in Samoa and Guam, according to the CDC.
Public-health experts were reminded of the disease’s persistent threat in 2010 when Puerto Rico reported the largest outbreak of dengue in its history, recording more than 21,000 reported cases. A year before, Florida had reported the first cases of local dengue transmission in 75 years, within Old Town, Key West, according to the CDC’s Feb. 16, 2011 issue of The Dengue Update.
For the military, dengue infections have the potential to wreak havoc on troops and military operations. CDC notes that symptoms include a high fever accompanied by at least two of the following symptoms: severe headache, severe eye pain (behind eyes), joint pain, muscle and/or bone pain, rash, mild bleeding manifestation (e.g., nose or gum bleed, petechiae or easy bruising) and low white-cell count
For deployed troops, there is, on average, a loss of eight or nine days of active-duty days for those who are infected with dengue, according to Porter, who added, “This means you can’t work, you can’t fight, you can’t do whatever.”
With no specific treatment for dengue infection, currently the best prevention method is to avoid mosquito bites. Even with use of the insecticide DEET and/or bednets, that is not always effective for troops.
“The unique thing about dengue is, unlike malaria, where the mosquito starts biting at dusk and throughout the night, the mosquito that transmits dengue bites during the day and prefers humans as opposed to any other kind of potential food source …,” Porter explained. “All the experts say the most effective and efficient way to protect against dengue is a vaccine, so you vaccinate troops before they go to a dengue-endemic area. And then they are protected.”