New dengue vaccine offers hope

A small study has found that a new type of dengue vaccine called TV003 seems to protect people against at least one type of the virus.

The clinical trial, in which volunteers were infected with dengue virus six months after receiving either an experimental dengue vaccine developed by scientists from the National Institutes of Health (NIH) or a placebo injection, yielded starkly contrasting results.

All 21 volunteers who received the vaccine, TV003, were protected from infection, while all 20 placebo recipients developed infection. The study underscores the importance of human challenge studies, in which volunteers are exposed to disease-causing pathogens under carefully controlled conditions.

"The findings from this trial are very encouraging to those of us who have spent many years working on vaccine candidates to protect against dengue, a disease that is a significant burden in much of the world and is now endemic in Puerto Rico," said Stephen Whitehead of NIH's National Institute of Allergy and Infectious Diseases (NIAID). "In fact, these results informed the recent decision by officials at Brazil's Butantan Institute to advance the TV003 vaccine into a large phase 3 efficacy trial."

The experimental vaccine was developed primarily by Dr. Whitehead and his colleagues at NIAID's Laboratory of Infectious Diseases. Scientists from the U.S. Food and Drug Administration also contributed to the vaccine's development.

The candidate vaccine is made from a mixture of four live, weakened (attenuated) viruses targeted to each of the four serotypes. A total of 48 healthy adult volunteers enrolled at two trial sites, the University of Vermont College of Medicine, Burlington, and Johns Hopkins Bloomberg School of Public Health, Baltimore, and were randomly assigned to receive either vaccine or placebo injection.

"Because there are no specific therapies for dengue fever, it is desirable to have a challenge virus that causes infection, but does not result in significant symptoms of disease," Anna Durbin, who led the clinical trial, said.

Dr. Whitehead is currently developing a human challenge model using a modified dengue serotype-3 virus. This challenge virus could be used in future clinical trials to test the efficacy of candidate dengue vaccines or therapies.

The study is published in Science Translational Medicine.