The world's first vaccine against dengue, developed by French drugmaker Sanofi, has shown the ability to protect against disease caused by three of four dengue virus strains in a keenly awaited clinical trial in Thailand.
Sanofi said on Wednesday the proof of efficacy was "a key milestone" in the 70-year quest to develop a viable dengue shot, adding the results also confirmed the safety profile of the vaccine candidate.
The mosquito-borne disease - also known as "breakbone fever" - is a threat to nearly 3 billion people and is caused by four different types of virus, none of which confers immunity from the others.
Sanofi's vaccine generated an antibody response for all four dengue virus types, but evidence of protection was only demonstrated against three of the four circulating in Thailand. Sanofi said researchers were carrying out analyses to understand the lack of protection for the fourth serotype.
The company's vaccine unit, Sanofi Pasteur, has already invested 350 million euros ($423 million) in a new French factory to make the three-dose vaccine and believes its product could generate 1 billion euros in yearly sales.
But uptake of the vaccine will depend on precisely how well doctors believe it can protect populations at risk in fast-expanding tropical cities from Rio to Manila, as well as travelers.
Sanofi gave no details on the level of protection in a brief statement. The full data are now being reviewed by scientific experts and public health officials, with detailed results to be published later this year.
Sanofi previously said it planned to present the findings at the annual meeting of the American Society of Tropical Medicine and Hygiene in Atlanta in November.
Large-scale late-stage Phase III clinical studies with 31,000 participants are under way with Sanofi's vaccine in 10 countries in Asia and Latin America.