A new experimental vaccine for dengue fever has succeeded in its first late-stage clinical trial. Making this the first vaccine ever for this disease that affects more than 100 million people every year. Drug manufacturer Sanofi said their study results showed that the vaccine reduced the incidence of dengue fever by 56 percent in a trial involving more than 10 000 children in Indonesia, Malaysia, the Philippines, Thailand and Vietnam. Final results are still to be released but the study has so far achieved its primary clinical endpoint and the safety profile is good. Dengue fever is caused by a virus transmitted by mosquitoes and affects people mainly in tropical and subtropical areas. The disease, also known as breakbone fever, can cause severe fever and intense joint and muscle pain. Serious cases can cause hemorrhagic fever, which is marked by bleeding and shock. These can be fatal, especially to children. A vaccine is much needed as there is no specific treatment for dengue and no preventive approach other than controlling the mosquitoes that transmit the disease.