Dengue Vaccine Shows 100 % Protection In Small Study; Spurs Phase 3 Trials

After proving elusive for decades, a dengue vaccine with promise of community level immunity has shown 100 percent success in a small trial.

The vaccine, developed by National Institutes of Health, reportedly protected 21 participants in the trial against a mild-form of dengue. The trial comprised 40 volunteers who were either given the vaccine or a placebo, before being exposed to the virus. All volunteers given placebo were infected.

"All 21 recipients of TV003 who were challenged with rDEN2Δ30 were protected from infection with rDEN2Δ30 [an attenuated variant of the virus]," researchers wrote in the journal Science Translational Medicine. "None developed viremia, rash, or neutropenia after challenge."

The vaccine, TV003, is in phase-2 clinical trials but its success in the small-sample study helped accelerate its progress to phase-3 clinical trials. The Washington Post reported a phase 3 trial had begun in Brazil last month with 17,000 participants including adolescents and children. The trial is expected to conclude in 2018 and if successful, could make the vaccine available across the world.

Spread by Aedes aegypti, Dengue virus is found in tropical regions of the world, infecting over 400 million every year. In some cases, the virus produces disease including hemorrhagic fever that can be fatal. Efforts to develop a vaccine have proven elusive as four serotypes exist of the virus. Until recently, vaccine candidates have not proven effective against all serotypes.

The small-sample study has also helped health scientists establish a human challenge model that can minimize risk of failure in large trials.

"TV003, a live attenuated dengue vaccine that induces antibodies to all four dengue virus serotypes, protected against infection of an attenuated virus in 21 recipients when compared with 20 non-vaccinated control," researchers wrote.

"This model may serve as an early check for dengue vaccine candidates, limiting the risk of conducting large unsuccessful trials."

Success of dengue vaccine trials is also expected to boost the development of a vaccine for zika, as both viruses share similarities.