News / Health

Test of New Dengue Vaccine Shows Promise

A boy with dengue fever receives medical oxygen while laying on a bed at the Quirino hospital in Quezon city in the suburbs of Manila, August 14, 2012.A boy with dengue fever receives medical oxygen while laying on a bed at the Quirino hospital in Quezon city in the suburbs of Manila, August 14, 2012.
x
A boy with dengue fever receives medical oxygen while laying on a bed at the Quirino hospital in Quezon city in the suburbs of Manila, August 14, 2012.
A boy with dengue fever receives medical oxygen while laying on a bed at the Quirino hospital in Quezon city in the suburbs of Manila, August 14, 2012.
TEXT SIZE - +
Faith Lapidus
A clinical trial of a new vaccine against dengue fever shows progress toward fighting the most common mosquito-borne disease.  The drug is less successful than hoped, but seems to be effective at preventing three of the four related viruses that cause dengue.

Dengue fever increasing

Dengue fever is endemic across the tropics, with more than 2.5 billion people in 128 countries at risk. Symptoms can range from aches and fever to circulatory failure, coma and death.  Some 21,000 people die of dengue each year, and the number of cases is increasing, including outbreaks in the southeastern United States.

There is no vaccine available to prevent dengue fever.  Part of the difficulty in developing one is that there are four different but related types of the disease.  Those who recover from infection by one type gain lifetime immunity, but only against that type.  Scott Halstead, of the Dengue Vaccine Initiative, explains that they are still at risk of infection with one of the other types.

"Dengue normally produces a short acute febrile disease, sort of a flu-like disease which ends in a rash, and when you're convalescent, you have life-long immunity to the type you've been infected with, say Type 1.  But you are susceptible then to either type 2 or 3 or 4, and what we've learned is that two different infections - with say, Type 1 and Type 2 - can result in a very severe catastrophic disease called dengue hemorrhagic fever, and this occurs all over the tropical world, mostly in Asia and the American tropics," Halstead explained.

New vaccine

That is why researchers are focused on developing a so-called tetravalent vaccine, modeled on the successful yellow fever vaccine, combining weakened versions of all four types of dengue virus into a single drug. 

Halstead, who was not involved in the new clinical trial, says the pharmaceutical company, Sanofi Pasteur, took a molecular approach to creating its vaccine.

"They actually spliced the gene for each of the four dengue viruses into a yellow fever backbone.  So this is a combined vaccine called a chimera, combining the yellow fever replicative machinery and the dengue surface proteins," he said. "But it is a vaccine mixture of dengue 1, 2, 3 and 4."

In the first trial to determine whether a vaccine could actually prevent the disease, Sanofi's drug was tested in 4,000 school children in Thailand.  The children got three doses of either the vaccine or a placebo.  Spacing the shots six months apart was meant to mimic the natural immune response people develop over time.  Two years later, the vaccine seemed to have protected the children against three of the four strains, but not the most common type of the virus, which accounts for about 40 percent of severe dengue cases worldwide.

But the results show that the vaccine is safe, and technologically possible.

Although Halstead and many other dengue experts expressed disappointment that Sanofi's vaccine was not more effective, they regard it as an important step forward.

"The problem is, can we use a vaccine that only protects against three?  In my commentary that I wrote for The Lancet, I speculated that maybe, if you could really give enough of a three-component vaccine to stop transmission, you'd actually leave just one virus, and one virus all by itself won't cause dengue hemorrhagic fever.  So a lot of the really serious problems caused by dengue viruses might be controlled with a three-component vaccine," said Halstead.

Sanofi is already testing its new vaccine in large Phase 3 trials involving more than 30,000 people in 10 countries, with results expected in 2014.  A report about the Phase 2 trial, and Dr. Halstead's commentary, appear in the medical journal, The Lancet.

You May Like

Russia-Ukraine Crisis Could Trigger Cyber War

As tensions between Kyiv and Moscow escalate, so too has frequency of online attacks targeting government, news and financial sites More

Egyptian Court Jails 23 Pro-Morsi Supporters

Meanwhile, Egyptian officials say gunmen have killed two members of the country's security forces More

Pakistani Journalists Protest Shooting of Colleague

Hamid Mir, a host for private television channel Geo, was wounded after being shot three times Saturday, but is expected to survive More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Ukraine, Russia, United in Faith, Divided in Politicsi
X
Michael Eckels
April 19, 2014
There is a strong historical religious connection between Russia and Ukraine. But what role is religion playing in the current conflict? In the run-up to Easter, Michael Eckels in Moscow reports for VOA.
Video

Video Ukraine, Russia, United in Faith, Divided in Politics

There is a strong historical religious connection between Russia and Ukraine. But what role is religion playing in the current conflict? In the run-up to Easter, Michael Eckels in Moscow reports for VOA.
Video

Video Face of American Farmer is Changing

The average American farmer is now 58 years old, and farmers 65 and older are the fastest growing segment of the population. It’s a troubling trend signaling big changes ahead for American agriculture as aging farmers retire. Reporter Mike Osborne says a new report from the U.S. Census Bureau is suggesting what some of those changes might look like... and why they might not be so troubling.
Video

Video Donetsk Governor: Ukraine Military Assault 'Delicate But Necessary'

Around a dozen state buildings in eastern Ukraine remain in the hands of pro-Russian protesters who are demanding a referendum on self-rule. The governor of the whole Donetsk region is among those forced out by the protesters. He spoke to VOA's Henry Ridgwell from his temporary new office in Donetsk city.
Video

Video Drones May Soon Send Data From High Seas

Drones are usually associated with unmanned flying vehicles, but autonomous watercraft are also becoming useful tools for jobs ranging from scientific exploration to law enforcement to searching for a missing airliner in the Indian Ocean. VOA’s George Putic reports on sea-faring drones.
Video

Video New Earth-Size Planet Found

Not too big, not too small. Not too hot, not too cold. A newly discovered planet looks just right for life as we know it, according to an international group of astronomers. VOA’s Steve Baragona has more.
Video

Video Copts in Diaspora Worry About Future in Egypt

Around 10 percent of Egypt’s population belong to the Coptic faith, making them the largest Christian minority in the Middle East. But they have become targets of violence since the revolution three years ago. With elections scheduled for May and the struggle between the Egyptian military and Islamists continuing, many Copts abroad are deeply worried about the future of their ancient church. VOA religion correspondent Jerome Socolovsky visited a Coptic church outside Washington DC.
Video

Video Critics Say Venezuelan Protests Test Limits of Military's Support

During the two months of deadly anti-government protests that have rocked the oil-rich nation of Venezuela, President Nicolas Maduro has accused the opposition of trying to initiate a coup. Though a small number of military officers have been arrested for allegedly plotting against the government, VOA’s Brian Padden reports the leadership of the armed forces continues to support the president, at least for now.
Video

Video More Millenials Unplug to Embrace Board Games

A big new trend in the U.S. toy industry has more consumers switching off their high-tech gadgets to play with classic toys, like board games. This is especially true among the so-called millenial generation - those born in the 1980's and 90's. Elizabeth Lee has more from an unusual café in Los Angeles, where the new trend is popular and business is booming.
Video

Video Google Buys Drone Company

In its latest purchase of high-tech companies, Google has acquired a manufacturer of solar-powered drones that can stay in the air almost indefinitely, relaying broadband Internet connection to remote areas. It is seen as yet another step in the U.S. based Web giant’s bid to bring Internet to the whole world. VOA’s George Putic reports.
AppleAndroid