It may take a few more months of clinical trials, but by 2015, researchers say the world may finally have a vaccine against dengue, a mosquito-borne illness that affects millions of people worldwide.
During its first trial phases, the dengue vaccine was considered imperfect, generating only slightly more than 60 percent protection for individuals being vaccinated. The latest trial–trial number three–has shown significantly more success, however, with researchers reporting 95.5 percent efficacy against the most severe form of the disease, dengue hemorrhagic fever.
The World Health Organization (WHO) indicates dengue hemorrhagic fever is a leading cause of hospitalization and death among children in many Latin American countries where the disease is prevalent. Unfortunately, prevention and treatment methods have only been able to focus on symptoms of the disease for people currently affected.
“Theres no vaccine for dengue currently, nor is there any specific treatment for managing illness in people who contract symptomatic dengue disease,” Alain Bernal, a spokesperson for Sanofi Pasteur, the drugs manufacturer and the trials sponsor, told The Verge. “These results show that our candidate vaccine has the potential to have a major public health impact.”
While the new vaccine was shown to be more than 95 percent effective against the most severe form of dengue, the results were not similar for engue serotypes I and II less severe forms of dengue where the efficacy rates were 50.3 percent and 42.3 percent, respectively. The third trial is still considered a huge success, since mild form of dengue rarely require hospitalization and generally present as flu-like symptoms. Many healthy adults and children have contracted milder forms of dengue and survived.
“Dengue should be suspected when a high fever (40°C/ 104°F) is accompanied by two of the following symptoms: severe headache, pain behind the eyes, muscle and joint pains, nausea, vomiting, swollen glands or rash. Symptoms usually last for 27 days, after an incubation period of 410 days after the bite from an infected mosquito,” states the WHO. “Dengue fever is a severe, flu-like illness that affects infants, young children and adults, but seldom causes death.”
The low mortality rate for mild forms of dengue negate the vaccine’s lower efficacy rates for those serotypes.
“It is not a perfect vaccine yet, but a promising one,” said Annelies Wilder-Smith, an epidemiologist at Nanyang Technological University in Singapore. “It is most important to protect against severe disease versus mild disease, so reduction by 95 percent is very good.”