The French pharmaceutical company Sanofi said on Monday that its experimental vaccine for dengue fever had succeeded in its first late-stage clinical trial. The results could help pave the way for the introduction of the first vaccine to prevent a disease that afflicts an estimated 50 million to 100 million people a year.
Sanofi said the vaccine reduced the incidence of dengue fever by 56 percent in a trial involving more than 10,000 children in Southeast Asia.
Outside experts said they were hoping for even greater effectiveness, but some said the vaccine could still be useful.
“I’m looking for something that could potentially do better than this,” said Dr. Robert Edelman, clinical professor of medicine and pediatrics at the University of Maryland. He said ideally a vaccine would be 80 percent effective, which would not only protect vaccinated individuals but also reduce transmission to unvaccinated people.