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.
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

On Everest, Helicopters Rescue Stranded Climbers

Choppers transport some of more than 100 mountaineers trapped after deadly quake, avalanches More

Video Ten Years After Riots, France Searches for Answers to Neglected Suburbs

In 2005, a Paris suburb exploded into violence after two teenagers were electrocuted as they hid from police; since then, somethings have changed, others not More

US, Japan Announce Historic Revision of Defense Cooperation Guidelines

Nations say new guidelines will be 'cornerstone for peace and security' in Asia-Pacific region while also serving as 'platform for a more stable international security environment' More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
‘Angel of the Migrants’ Helps Desperate Syrians Arriving in Europei
X
Henry Ridgwell
April 26, 2015 10:36 PM
Waves of migrants are continuing to arrive on the shores of southern Italy from North Africa. After their dangerous journey across the Mediterranean, they face an unknown future in Europe. In the Sicilian city of Catania there is an activist dedicated to helping the refugees on their journey.
Video

Video ‘Angel of the Migrants’ Helps Desperate Syrians Arriving in Europe

Waves of migrants are continuing to arrive on the shores of southern Italy from North Africa. After their dangerous journey across the Mediterranean, they face an unknown future in Europe. In the Sicilian city of Catania there is an activist dedicated to helping the refugees on their journey.
Video

Video Ten Years After Riots, France Searches for Answers to Neglected Suburbs

January’s terrorist attacks and fears of more to come are casting a spotlight on France’s neglected suburbs. Home to many immigrants, and sometimes hubs of crime, they were rocked by rioting a decade ago. Lisa Bryant visited the Paris suburb of Clichy-sous-Bois, where the 2005 violence first broke out, and has this report about what has changed and what has not.
Video

Video Gay Marriage Goes Before US Supreme Court

This week, the U.S. Supreme Court will hear arguments on whether gay people have a constitutional right to marriage. VOA’s Michael Bowman reports, the case could lead to the nationwide legalization of same-sex marriage, or a continuation of the status quo in which individual states decide whether to recognize gay unions.
Video

Video Study: Insecticide Damaging Wild Bee Populations

A popular but controversial type of insecticide is damaging important wild bee populations, according to a new study. VOA’s Steve Baragona has more.
Video

Video Data Servers Could Heat Private Homes

As every computer owner knows, when their machines run a complex program they get pretty hot. In fact, cooling the processors can be expensive, especially when you're dealing with huge banks of computer servers. But what if that energy could heat private homes? VOA’s George Putic reports that a Dutch energy firm aims to do just that.
Video

Video Cinema That Crosses Borders Showcased at Tribeca Film Festival

Among the nearly 100 feature length films being shown at this year’s Tribeca Film Festival in New York City are more than 20 documentaries and features with international appeal, from a film about a Congolese businessman in China, to documentaries shot in Pakistan and diaspora communities in the U.S., to a poetic look at disaffected South African youth. VOA’s Carolyn Weaver has more.
Video

Video UN Confronts Threat of Young Radicals

The radicalization and recruitment of young people into Islamist extremist groups has become a growing challenge for governments worldwide. On Thursday, the U.N. Security Council heard from experts on the issue, which has become a potent threat to international peace and security. VOA’s Margaret Besheer reports.
Video

Video Growing Numbers of Turks Discover Armenian Ancestry

In a climate of improved tolerance, growing numbers of people in Turkey are discovering their grandmothers were Armenian. Hundreds of thousands of Armenians escaped the mass deportations and slaughter of the early 1900's by forced conversion to Islam. Or, Armenian children were taken in by Turkish families and assimilated. Now their stories are increasingly being heard. Dorian Jones reports from Istanbul that the revelations are viewed as an important step.
Video

Video Migrants Trek Through Western Balkans to Reach EU

Migrants from Africa and other places are finding different routes into the European Union in search of a better life. The Associated Press followed one clandestine group to document their trek through the western Balkans to Hungary. Zlatica Hoke reports that the migrants started using that route about four years ago. Since then, it has become the second-most popular path into Western Europe, after the option of sailing from North Africa to Italy.
Video

Video US Businesses See Cuba as New Frontier

The Obama administration's opening toward Cuba is giving U.S. companies hope they'll be able to do business in Cuba despite the continuation of the U.S. economic embargo against the communist nation. Some American companies have been able to export some products to Cuba, but the recent lifting of Cuba's terrorism designation could relax other restrictions. As VOA's Daniela Schrier reports, corporate heavy hitters are lining up to head across the Florida Straits - though experts urge caution.
Video

Video Kenya Launches Police Recruitment Drive After Terror Attacks

Kenya launched a major police recruitment drive this week as part of a large-scale effort to boost security following a recent spate of terror attacks. VOA’s Gabe Joselow reports that allegations of corruption in the process are raising old concerns about the integrity of Kenya’s security forces.
Video

Video Japan, China in Race for Asia High-Speed Rail Projects

A lucrative competition is underway in Asia for billions of dollars in high-speed rail projects. Cambodia, India, Indonesia, Malaysia Thailand and Vietnam are among the countries planning to move onto the fast track. They are negotiating with Japan and the upstart Chinese who are locked in a duel to revolutionize transportation across Asia. VOA Correspondent Steve Herman in Bangkok has details.
Video

Video Scientists: Mosquitoes Attracted By Our Genes

Some people always seem to get bitten by mosquitoes more than others. Now, scientists have proved that is really the case - and they say it’s all because of genes. It’s hoped the research might lead to new preventative treatments for diseases like malaria, as Henry Ridgwell reports from London.
Video

Video Bible Museum Coming to Washington DC

Washington is the center of American political power and also home to some of the nation’s most visited museums. A new one that will showcase the Bible has skeptics questioning the motives of its conservative Christian funders. VOA religion correspondent Jerome Socolovsky reports.
Video

Video Afghan First Lady Pledges No Roll Back on Women's Rights

Afghan First Lady Rula Ghani, named one of Time's 100 Most Influential, says women should take part in talks with Taliban. VOA's Rokhsar Azamee has more from Kabul.

VOA Blogs