Dengue Fever Vaccine Shows Some Promise in Trial
But experts would still like to see a more effective vaccine developed
Wilder-Smith, who authored an accompanying journal editorial, noted that other dengue vaccines are being tested, but it will take several years before those vaccines reach phase 3 trials.
"For the time being, this is the best and the only one we have," she said of the current vaccine, known as CYD-TDV.
The report, from scientists at the Research Institute for Tropical Medicine in the Philippines, was published online July 11 in The Lancet.
Dr. Marcelo Laufer, an infectious diseases specialist at Miami Children's Hospital, said he was "not impressed" by the efficacy of the vaccine.
Laufer also noted that the vaccine needs to be tested in other areas, particularly in Latin America, and that patients need to be followed for at least five years.
"I am curious to see how the vaccine would work in different populations," he said.
The trial, funded by vaccine maker Sanofi Pasteur, focused on children aged 2 to 14. They were randomly assigned to receive three injections of the CYD-TDV vaccine or a placebo vaccine.
After the first vaccination, the second was given six months later and the third six months after that. The children were followed for up to two years.
More than 28 days after the third vaccination, 117 children who received the vaccine developed dengue, compared with 133 who were given placebo. That works out to a vaccine effectiveness rate of 56.5 percent, the researchers noted.
In addition, after three doses, the vaccine was 88.5 percent effective against severe disease, which often leads to hospitalization for over 500,000 people -- mostly children -- every year.
"One of the difficulties in making a dengue vaccine is that you have to cover for four different viruses at the same time," Sharp explained. "If you are not able to do that, you risk increasing the chances of developing severe dengue."
The vaccine wasn't equally effective against all four dengue viruses. It was only 35 percent effective against type 2, more than 75 percent effective against types 3 and 4, and 50 percent effective against type 1.
The vaccine was well tolerated, the researchers reported. A total of 402 serious adverse events were reported in the vaccine group and 245 were reported in the placebo group.