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

Elusive Deal With Iran Could Yield Foreign Policy Legacy for Obama

A new Iranian leader -- and a strategic shift by the United States -- opens narrow window for nuclear agreement with Tehran More

Column: Saudi-Iran Meeting Could Boost Fight Against Islamic State

The fact that Iranians and Saudis are talking again does not guarantee a breakthrough, but it could make it easier to build a broad coalition against IS More

Thai Ruler Gives Top Cabinet Posts to Junta Inner Circle

Thailand's army chief has kept an iron grip on power as he extends the government, hand-picking an interim parliament that subsequently nominated him prime minister More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
West Africa Ebola Vaccine Trials Possible by Early 2015i
X
Carol Pearson
August 30, 2014 7:14 PM
A U.S. health agency is speeding up clinical trials of a possible vaccine against the deadly Ebola virus that so far has killed more than 1,500 people in West Africa. If successful, the next step would be a larger trial in countries where the outbreak is occurring. VOA's Carol Pearson has more.
Video

Video West Africa Ebola Vaccine Trials Possible by Early 2015

A U.S. health agency is speeding up clinical trials of a possible vaccine against the deadly Ebola virus that so far has killed more than 1,500 people in West Africa. If successful, the next step would be a larger trial in countries where the outbreak is occurring. VOA's Carol Pearson has more.
Video

Video Survivors Commemorate 70th Anniversary of Nazi Liquidation of Jewish Ghetto

When the German Nazi army occupied the Polish city of Lodz in 1939, it marked the beginning of a long nightmare for the Jewish community that once made up one third of the population. Roughly 200,000 people were forced into the Lodz Ghetto. Less than 7,000 survived. As VOA’s Kane Farabaugh reports, some survivors gathered in Chicago on the 70th anniversary of the liquidation of the Lodz Ghetto to remember those who suffered at the hands of the Nazi regime.
Video

Video Cost to Raise Child in US Continues to Rise

The cost of raising a child in the United States continues to rise. In its latest annual report, the U.S. Department of Agriculture says middle income families with a child born in 2013 can expect to spend more than $240,000 before that child turns 18. And sending that child to college more than doubles that amount. VOA’s Deborah Block visited with a couple with one child in Alexandria, Virginia, to learn if the report reflects their lifestyle.
Video

Video Chaotic Afghan Vote Recount Threatens Nation’s Future

Afghanistan’s troubled presidential election continues to be rocked by turmoil as an audit of the ballots drags on. The U.N. says the recount will not be completed before September 10. Observers say repeated disputes and delays are threatening the orderly transfer of power and could have dangerous consequences. VOA correspondent Meredith Buel reports.
Video

Video Ukraine Battles Pro-Russia Rebel Assault

After NATO concluded an emergency meeting to discuss the crisis in eastern Ukraine, the country is struggling to contain heavy fighting near the strategic port of Mariupol, on the Azov Sea. Separatist rebels are trying to capture the city, allegedly with Russian military help, and Ukraine's defense forces are digging in. VOA's Daniel Schearf spoke with analysts about what lies ahead for Ukraine.
Video

Video Growing Business Offers Paint with a Twist of Wine

Two New Orleans area women started a small business seven years ago with one thing in mind: to help their neighbors relieve the stress of coping with a hurricane's aftermath. Today their business, which pairs painting and a little bit of wine, has become one of the fastest growing franchises across the U.S. VOA’s June Soh met the entrepreneurs at their newest franchise location in the Washington suburbs.
Video

Video Ebola Vaccine Trials To Begin Next Week

The National Institutes of Health says it is launching early stage trials of a vaccine to prevent the Ebola virus, which has infected or killed thousands of people across West Africa. The World Health Organization says Ebola could infect more than 20,000 people across the region by the time the outbreak is over. The epidemic has health experts and governments scrambling to prevent more people from becoming infected. Zlatica Hoke has more.
Video

Video Asian Bacteria Threatens Florida Orange Trees

Florida's citrus fruit industry is facing a serious threat from a bacteria carried by the Asian insect called psyllid. The widespread infestation again highlights the danger of transferring non-native species to American soil. VOA’s George Putic reports.
Video

Video Aging Will Reduce Economic Growth Worldwide in Coming Decades

The world is getting older, fast. And as more people retire each year, fewer working-age people will be there to replace them. Bond rating agency Moody’s says that will lead to a decline in household savings; reducing global investments - which in turn, will lead to slower economic growth around the world. But experts say it’s not too late to mitigate the economic impact of the world’s aging populations. Mil Arcega has more.
Video

Video Is West Doing Enough to Tackle Islamic State?

U.S. President Barack Obama has ruled out sending ground troops to Iraq to fight militants of the so-called Islamic State, or ISIS, despite officials in Washington describing the extremist group as the biggest threat the United States has faced in years. Henry Ridgwell reports from London on the growing uncertainty over whether the West’s response to ISIS will be enough to defeat the terrorist threat.
Video

Video Coalition to Fight Islamic State Could Reward Assad

The United States along with European and Mideast allies are considering a broader assault against Islamic State fighters who have spread from Syria into Iraq and risk further destabilizing an already troubled region. But as VOA State Department Correspondent Scott Stearns reports, confronting those militants could end up helping the embattled Syrian President Bashar al-Assad.
Video

Video Made in America Socks Get Toehold in Online Fashion Market

Three young entrepreneurs are hoping to revolutionize the high-end sock industry by introducing all-American creations of their own. And they’re doing most of it the old-fashioned way. VOA’s Julie Taboh recently caught up with them to learn what goes into making their one-of-a-kind socks.
Video

Video Americans, Ex-Pats Send Relief Supplies to West Africa

Health organizations from around the world are sending supplies and specialists to the West African countries that are dealing with the worst Ebola outbreak in history. On a smaller scale, ordinary Americans and African expatriates living in the United States are doing the same. VOA's Carol Pearson reports.

AppleAndroid