LONDON, Sept. 15 (UPI) -- A new dengue fever vaccine under development is a step forward but not as effective as hoped, a clinical trial carried out in Thailand found.
Tests show the drug, which would be the first vaccine for the fever, appears effective at preventing three of the four related viruses that trigger the disease, Voice of America reports.
About 21,000 people die of dengue fever annually. Symptoms include aches, fever, circulatory failure, then coma and death.
Scott Halstead of the Dengue Vaccine Initiative, who was not part of the clinical trial, notes vaccine developer Sanofi Pasteur, a French pharmaceutical company, used a molecular approach to creating the drug.
"They actually spliced the gene for each of the four dengue viruses into a yellow fever backbone," he said. "So this is a combined vaccine called a chimera, combining the yellow fever replicative machinery and the dengue surface proteins. But it is a vaccine mixture of dengue 1, 2, 3 and 4."
The vaccine was tested for a two-year period in 4,000 school children in Thailand. The vaccine appeared to protect against three of the four strains, but not the most common type, which accounts for about 40 percent of severe dengue cases worldwide, VOA said.
The vaccine was found to be safe and technologically feasible, the network said. Halstead said controlling three strains may successfully ward off "really serious problems."
VOA said Sanofi Pasteur is testing its vaccine in large Phase 3 trials involving more than 30,000 people in 10 countries. The results of those tests are expected in 2014.
A report about the Phase 2 trial appeared in the British medical journal The Lancet.