- A new dengue vaccine protects people against at least one type of dengue virus in a small study
- A clinical trial in Brazil is testing whether the vaccine can reduce dengue in children and adults
- Another dengue vaccine called Dengvaxia has been licensed in four countries
Although another dengue vaccine recently became available in Mexico, Brazil, the Philippines and El Salvador, it may not be appropriate to use in countries such as the United States.
That licensed vaccine, called Dengvaxia, has been found to reduce the rates of severe dengue cases in adults and older children in Asia and Latin America, but many of them had probably already had a dengue infection in their lives. In contrast, Dengvaxia
could increase the risk of dengue disease among young children who have not been exposed to dengue virus before -- a group that is similar to the U.S. population. (In countries where the vaccine is available, it is only given to children age 9 and older.)
So researchers at several institutions in the United States set out to develop a new vaccine that would give people -- including those who have not been infected -- strong protection against all four types of dengue virus.
"Control of dengue has certainly been a public health priority for many years. But getting there has not been easy," Stephen S. Whitehead, a researcher at the National Institutes of Health who designed the new vaccine, said at a news teleconference on Tuesday. Whitehead is one of the authors of the study that tested TV003, which was published on Wednesday in Science Translational Medicine
The researchers decided to take a different tack in testing the vaccine. Normally the efficacy of a new vaccine is tested in large studies in areas affected by the disease, but those kinds of studies can take up to 10 years and cost millions of dollars. Although that research will still need to be done, "we really wanted to have an early clue that the (vaccine) would work," Whitehead said.
A different way to test vaccines
Instead, the researchers used a "human challenge model." They gave TV003 to 24 adult volunteers in Maryland and Vermont, while another 24 adults got a placebo as a control. After one injection of TV003, 92% of participants in the vaccine group developed antibodies to all four types of dengue virus. The only side effect associated with the vaccine was a rash around the injection site, which typically went away in five to 10 days.
But the biggest question is whether the new vaccine can prevent dengue infections. In the "human challenge" part of the study, the participants were artificially infected -- using a needle, instead of a mosquito -- six months after receiving TV003 with a highly weakened version of dengue virus Type 2.