Sanofi Pasteur, the vaccines division of Sanofi announced this week in The Lancet the detailed results of  its first landmark phase III dengue vaccine efficacy study conducted in five countries in Asia. Results show overall efficacy against symptomatic dengue of 56.5% in children aged 2 to 14 years old after a three-dose vaccination schedule. Importantly, analyses show an 88·5% reduction of dengue hemorrhagic fever, the severe form of dengue, according to the WHO criteria. The study also showed a clinically important reduction in the risk of hospitalization due to dengue by 67% during the study. The favorable vaccine safety profile observed during the 25 month follow up of the phase III study in Asia is consistent with the safety profile documented in other studies (phase I, II, IIb).


Dengue is a threat to nearly half the world’s population, and is a pressing public health priority in many countries in Asia and Latin America where epidemics occur. The study confirmed the very high burden of disease by revealing that one in twenty children in the control group suffered from dengue each year, which was three-fold higher than initially expected. Each year, an estimated 500,000 people, including children, have severe dengue requiring hospitalization. This puts huge strain on hospitals and health care systems during outbreaks.

“The results of this first phase III study show the potential of the vaccine to have a significant impact on public health,” commented Dr. Maria Rosario Capeding, study principal investigator, Research Institute for Tropical Medicine, the Philippines. “The threat of severe dengue disease creates fear in the community. The vaccine’s impact on preventing dengue hemorrhagic fever is noteworthy. A vaccine that is able to avoid the personal suffering and reduce this significant health burden would change the lives of millions.”

Safety analyses (solicited reactions, unsolicited events and Serious Adverse Events SAEs) during the study showed similar reporting rates between the vaccine and control groups. SAEs were consistent with medical disorders in this age group and were mainly infections and injuries. Safety is continuously reviewed by an independent data monitoring committee. To date, 27,000 children, adolescents and adults have been vaccinated with three doses of the candidate dengue vaccine throughout the clinical studies.

“The high efficacy observed against severe dengue and the reduction of hospitalization by two thirds is an extremely important public health outcome. Furthermore this dengue vaccine continues to meet the highest safety expectations, which is very reassuring,” commented Professor Duane Gubler, Professor and Founding Director of the Signature Research Program on Emerging Infectious Diseases, Duke-NUS Graduate Medical School, Singapore, and Chairman of the Partnership for Dengue Control.

“These pivotal phase III vaccine efficacy study results take us closer to our ambition to bring the first vaccine against dengue to the world,” said John Shiver, Senior Vice President, R&D at Sanofi Pasteur. “After more than 20 years of commitment in collaboration with the scientific community, we are on course to make dengue the next vaccine-preventable disease. The public-health implications of a future dengue vaccine are significant and these findings are an important stride towards meeting the WHO’s strategic goals of reducing dengue mortality by half and morbidity by at least 25% by 2020.”

The four dengue virus serotypes have circulated during the study with a distribution representative of the epidemiology in Asia. The measured efficacy of the vaccine during the 25 months observation of the study is consistent across countries and appears to vary by dengue serotype (between 34.7% and 72.4%) and by age. The results of this first, large-scale efficacy study will be supplemented by results from a second, large-scale phase III study in Latin America and the Caribbean, including more than 20,000 children and adolescents aged 9 to 16 years old from Brazil, Colombia, Honduras, Mexico and Puerto Rico.


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