Human trials of an experimental dengue fever vaccine have just concluded, and the experimental compound looks promising in offering protection against the complex mosquito-borne illness that afflicts millions of people living in tropical and sub-tropical regions.
Dengue fever, spread by the bite of an infected Aedes mosquito, is caused by four different but related viruses, making the development of a vaccine difficult, according to Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.
“The problem with a dengue vaccine is that unlike other viruses where if you get infected with one or vaccinated with one you’re protected, period, after you recover. Whereas with dengue since there are four types, a vaccine needs to protect you against all four, because if you are only protected against one or two, you are still susceptible to one or the other of the three or four viruses,” Fauci said.
The U.S. government-funded trial was small, involving 112 healthy men and women between the ages of 18 and 50. The purpose was to see whether the experimental vaccine, made up of live but weakened viruses, was both safe and stimulated an antibody response against all four dengue types.
Researchers at Johns Hopkins School of Public Health in Baltimore, Maryland formulated four different versions of the combination vaccine, and tested a separate vaccine in each of four groups of 20 study participants. All of the dengue vaccines produced an antibody response. But one experimental compound, called TV003, induced an immune response against all four dengue viruses in 45 percent of participants. And an immune response to three viruses was seen in about 90 percent of participants.
The combination vaccine was safe, producing only a faint rash in about 60 percent of the participants, according to Fauci.
“I’m cautiously optimistic that we will have a vaccine after a period of time. But again, this is in [the very early] stages - only a Phase One trial,” Fauci said.
The experimental dengue vaccine will undergo more safety and effectiveness testing in Phase 2 and Phase 3 trials, with researchers looking to see how well it creates an immune response against all four dengue viruses in Brazil and Thailand, where the mosquito-borne illness is endemic.
Dengue fever, also known as break bone fever, infects an estimated 50 million to 00 million people in developing countries each year. Experts say the vaccine should cost less than $1 dollar a dose to produce, making it accessible to developing countries most impacted by the disease.