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Dengue Vaccine Shown to Cut Infections, Hospitalizations

Aedes aegypti mosquito

Aedes aegypti mosquito that carries Dengue fever (

11 July 2014. A large-scale clinical trial of a vaccine by the pharmaceutical company Sanofi shows the vaccine prevents symptomatic dengue cases by more than half, with severe forms and hospitalizations from the disease reduced even further. Findings from the study, conducted among more than 10,000 children in five Asian countries, are reported online today in the journal The Lancet (paid subscription required).

Dengue is viral disease transmitted by infected mosquitoes (not person-to-person) that occurs most frequently in tropical urban regions of the world. World Health Organization estimates from 50 to 100 million dengue infections occur each year, with half of the world’s population at risk. WHO says the disease is now endemic in more than 100 countries, especially in Asia, Africa, the Americas, eastern Mediterranean, and Pacific islands.

The disease is a collection of four major types, but all types can cause high fever, severe headache, muscle and bone pain, and bleeding. Dengue hemorrhagic fever is a severe form of the disease that can cause respiratory problems, severe bleeding, and organ failure, and become fatal. There are no treatments for dengue other than caring for symptoms, and up to now, no vaccines to prevent its occurrence.

Sanofi says its Sanofi Pasteur division worked on a dengue vaccine for more than 20 years. The vaccine is a live, but weakened virus that can still generate antibodies in the recipient, and covers all four types of dengue.

The clinical trial enrolled 10,275 children age 2 to 14 in dengue-endemic regions of Indonesia, Malaysia, Philippines, Thailand, and Vietnam. Participants were randomly divided on a 2 to 1 ratio between those receiving injections with the vaccine or a placebo, in 3 doses each 6 months apart.

The trial looked mainly for the number of children developing confirmed dengue infections and symptoms, after 28 days following the last injection. Of the entire sample, 250 children developed dengue: 117 or 1.7 percent of the cases were in group receiving the vaccine and 133 or 3.9 percent were in the group receiving the placebo, a rate 56 percent lower in the vaccine group.

Further analysis of the results shows participants receiving the vaccine were 88.5 percent less likely to develop dengue hemorrhagic fever, the severe form of the disease. In addition, the risk of hospitalization from dengue was reduced by two-thirds (67%) in the vaccine group.

The researchers tallied 647 serious adverse events, mainly infections and injuries, during the trial. Some 6 in 10 (62%) serious reactions occurred among the vaccine recipients, compared to 38 percent in the placebo group. However, only about 1 percent of each group developed serious reactions within 28 days of the injections.

“The threat of severe dengue disease creates fear in the community,” says study director Maria Rosario Capeding of the Research Institute for Tropical Medicine in the Philippines, in a Sanofi statement. “A vaccine that is able to avoid the personal suffering and reduce this significant health burden would change the lives of millions.”

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Hat tip: FirstWord Pharma

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