How does dengue fever kill

The Mexican health authorities were the first in the world to approve a vaccine against dengue fever. The disease is caused by a virus and, like malaria, is transmitted by mosquitoes. It is one of the greatest threats to global health. According to the World Health Organization, at least 50 to 100 million people are infected with the tropical virus every year. The hardest hit are Southeast Asia and Central and Latin America. Sick people suffer from fever and cramps, and rarely from internal bleeding.

In Mexico, the number of infections has increased almost a hundredfold since the turn of the millennium. In 2014, almost 125,000 people fell ill in the Central American state. The course of the disease is seldom severe and even more rarely fatal. But the social and economic burdens are assessed as enormous. For years there has been pressure to develop a vaccine. Of the six candidates, the now approved drug Dengvaxia from the pharmaceutical manufacturer Sanofi had long been considered particularly promising. The vaccination covers all four known virus types.

Snowball effect through vaccination?

However, Dengvaxia does not offer perfect protection: The preparation only lowers the risk of illness by around 60 percent. However, model calculations are said to have shown that even a few vaccinations for dengue could limit the transmission of the virus, because the mosquitoes then transmit infected blood less often.

According to the pharmaceutical manufacturer, this could cause the vaccine to trigger a snowball effect. A study shows that the vaccine reduces the risk of illness in children and adolescents between the ages of nine and 16 years by as much as two thirds, i.e. slightly more significantly.

"The bumpy search continues"

Dengue is particularly dangerous for even younger children because their immune system is immature and therefore often unable to defeat the virus. Playing in the mud and by rivers and lakes increases the risk of a mosquito bite. The result: Dengue fever kills the offspring in particular - and it is not yet clear whether the new vaccine will work reliably for babies and toddlers up to nine years of age.

This is the result of two studies in which the vaccine was tested on more than 31,000 children in Latin America and Asia. "The bumpy search for a solution continues," wrote Cameron P. Simmons of Melbounre University in a comment in the New England Journal of Medicine.

Jonas Schmidt-Chanasit from the Bernhard Nocht Institute for Tropical Medicine questions whether the new active ingredient will actually be a success. Since three vaccinations are necessary, the price is rising and many people in the countryside may not be able to benefit from it, the expert said. "Perhaps it would be better to put the money in hospitals so that nobody has to die of dengue fever", says Schmidt-Chanasit.

The pharmaceutical manufacturer Sanofi is meanwhile planning approval of the product in the EU as well. The virus has not yet really made its home here, but the vector, the mosquitoes, are spreading further into subtropical regions with climate change. Infections have already been reported in southern France and Croatia, although the circumstances surrounding these diseases are not fully understood.