Results from an early test of a dengue vaccine suggest it isn't ideal, but scientists say the study is still encouraging news in the global fight against the disease known as "break-bone fever."
There is currently no treatment or vaccine for dengue, which causes symptoms including fever, severe joint pain, headache and bleeding. The mosquito-borne disease infects up to 100 million people worldwide every year, mostly in Asia, Africa and Latin America.
The research "provides the first evidence we could actually develop an effective vaccine against dengue," said Orin Levine, a professor at Johns Hopkins Bloomberg School of Public Health. He was not connected to the study, published online Tuesday by the journal Lancet.
"This is a milestone, but we're not there yet," he said.
Larger studies in about 30,000 people are now under way and should provide more information about the effectiveness of the vaccine made by Sanofi Aventis SA. Other dengue vaccines are being developed but Sanofi's is the furthest along.
The Sanofi vaccine was tested in more than 3,600 Thai children ages 4 to 11. More than 2,400 got three injections of the vaccine six months apart while about 1,200 got a rabies vaccine or a dummy shot. The study was paid for by Sanofi.
During about two years of follow-up, there were 134 dengue cases, including five severe cases. In the vaccine group, about 3 percent got dengue, compared to about 4 percent in the group that didn't get the shot. The difference wasn't big enough to suggest any benefit from getting the vaccine.
Scientists said the vaccine seemed partly effective against three of the four viruses that cause dengue and no unusual side effects were reported. The study took place during an outbreak of mostly type 2 dengue, which causes the most serious disease, but the vaccine didn't work against that kind.
"It's not exactly a slam dunk," said Scott Halstead, a senior scientific adviser for the Dengue Vaccine Initiative, who wrote an accompanying commentary. He said Sanofi might need to consider reformulating the vaccine or creating separate shots for each type of dengue.
Joachim Hombach, a dengue expert at the World Health Organization, said it was encouraging that the vaccine appeared safe. "But the public health value of this vaccine remains to be demonstrated," he said.