Dengue also infamous as the break-bone fever, is a mosquito – borne viral disease. High fever, headache, severe ache behind the eyes, muscle and joint pains and rash similar to measles are the most common symptoms of Dengue. This disease is self limiting and no specific drug or treatment is available. Antibiotics don’t work and one has to simply rely on paracetamol and supportive therapies like oral re-hydration for mild disease or intravenous re-hydration for severe cases. Sometimes, Dengue takes the serious turn leading to internal bleeding, low level of blood platelets and extremely low blood pressure. Such cases of hemorrhagic dengue fever requires hospitalization and can even be fatal.
Dengue has become a global problem now, with 110 countries coming under endemic belt, where dengue virus can be transmitted. On an average, 50 million infections occur each year with about 500,000 severe hemorrhagic cases and 22,000 deaths. The numbers are increasing every year and the most affected age group is young children. Prevention of Dengue is the only wise option in absence of specific cure. Dengue vaccine is the most sought after vaccine today, in such a scenario.
Aedes aegypti mosquito is the main culprit in spreading the Dengue virus. There are four closely related Dengue viruses and infection with one type usually give lifelong immunity from reinfection with only that specific virus. But, it provides very less or no immunity from infections with other types of Dengue virus. In fact, the subsequent infections with different viruses later, typically increases the risk of severe complications. Due to the complex nature of this disease, vaccine development research aims at generation of tetravalent vaccine for providing long term protection against all types of Dengue viruses.
A candidate tetravalent dengue vaccine CYD-TDV developed by Sanofi Pasteur has shown positive results in three clinical trials involving 35,000 children in the age group 2-16 years from Asian and Latin American countries. According to a study published in “The New England Journal of Medicine”, this candidate vaccine was successful in reducing the risk of dengue related hospitalization for ~ 2 years after complete immunization with 3 doses amongst the 9 year and older participants who were vaccinated as compared to the control non vaccinated ones. This vaccine however didn’t prove to be as effective in the children below 9 years of age. The reason may be that this vaccine is ineffective in sensitizing the immature immune system of the young children. More research and trials will be needed to get the right vaccine for young children, who are the ones most badly hit by Dengue worldwide.