News / Health

New Malaria Vaccine Passes Safety Test

Researchers focus on improving effectiveness

Adult mosquitoes feeding on human blood containing malaria parasite.
Adult mosquitoes feeding on human blood containing malaria parasite.


Art Chimes

The fight against malaria may have taken a promising step forward with the latest tests of a new kind of vaccine, which aims to keep people healthy and prevent the infection from spreading.

Most malaria vaccines under development work by including genetically engineered versions of just a handful of the thousands of proteins of the Plasmodium parasite. Those modified proteins are designed to trigger an immune response to Plasmodium, after it’s passed into the host’s bloodstream by the bite of an infected mosquito.

In contrast, says researcher Robert A. Seder of the U.S. National Institute of Allergy and Infectious Diseases, this new vaccine includes a deactivated version of the entire parasite.

"So instead of picking out one or two or three genes," he says, "you have the potential for what we call breadth - generating an immune response that would be broad rather than narrower. And so that would be a good thing."

Sanaria staff produces the PfSPZ vaccine in the company's clinical manufacturing facility.
Sanaria staff produces the PfSPZ vaccine in the company's clinical manufacturing facility.

Plasmodium goes through many stages in its life cycle. To make this vaccine, scientists use the parasite at the stage - called the sporozoite - when it's ready to infect new hosts. They remove the sporozoite from the mosquito's salivary glands and then subject it to radiation.

That weakens it, so it can't cause malaria symptoms, and can't be transmitted via mosquito to another person, either.

This concept has been known since the 1960s, but Seder says there were practical obstacles that prevented the development of a malaria vaccine.

"The major breakthrough here was that my collaborator, Stephen Hoffman at [vaccine company] Sanaria, developed a method where he could isolate the sporozoites and purify them so that they could administer it as a vaccine to humans. And no one thought that that was possible," he explained.

Adult mosquitoes ready for vaccine production.
Adult mosquitoes ready for vaccine production.

And no one knew if the weakened sporozoites would jump-start the immune system to protect against malaria.

To find out, researchers used human volunteers. The vaccine was injected into their skin with a needle, to simulate the bite of a mosquito. From a safety standpoint, the results were good - there were only relatively minor side effects. But a vaccine must be safe and effective, and this one just wasn't very effective. Only two out of 44 volunteers who got the vaccine were protected when bitten by malaria-infected mosquitoes.

To find out why, the researchers then switched to laboratory animals, and Seder says they concluded that the problem was the way the vaccine was administered.

"Had [Hoffman] given [the vaccinations] in the vein, intravenously, directly in the blood, rather than through the skin, he would have gotten much higher immune responses."

That would be unusual for a vaccine, which is typically given by mouth or as a skin or muscle injection. It also might complicate mass vaccination programs, if the vaccine goes into general use.

Cost is also an issue, but researcher Seder says it's too soon to know how the vaccine will be priced - assuming it is effective.

The next stage of human testing - using intravenous administration - is due to start in October.

You May Like

Syrian Rebels Poised for Anti-Russia Collaboration

Forty-one insurgent groups issue joint statement vowing retaliation for Russian air offensives More

Political Maneuver Revives Export-Import Bank's Chances

Parliamentary tactic gets bill out of committee, but it faces opposition in the Senate More

Beijing Warns US on S. China Sea Patrols

Warning follows news reports Thursday that US military is planning to sail warships close to artificial islands Beijing has been aggressively building More

This forum has been closed.
There are no comments in this forum. Be first and add one

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
House Republicans in Chaos as Speaker Favorite Withdrawsi
Jim Malone
October 09, 2015 12:32 AM
The Republican widely expected to become the next speaker of the House of Representatives shocked his colleagues Thursday by announcing he was withdrawing his candidacy. The decision by Majority Leader Kevin McCarthy means the race to succeed retiring Speaker John Boehner is now wide open. VOA National Correspondent Jim Malone reports.

Video House Republicans in Chaos as Speaker Favorite Withdraws

The Republican widely expected to become the next speaker of the House of Representatives shocked his colleagues Thursday by announcing he was withdrawing his candidacy. The decision by Majority Leader Kevin McCarthy means the race to succeed retiring Speaker John Boehner is now wide open. VOA National Correspondent Jim Malone reports.

Video German, US Officials Investigate Volkswagen

German officials have taken steps to restore some of the reputation their car industry has lost after a recent Volkswagen diesel emissions scandal. Authorities have searched Volkswagen headquarters and other locations in an effort to identify the culprits in the creation of software that helps cheat on emission tests. Meanwhile, a group of lawmakers in Washington held a hearing to get to the bottom of the cheating strategy that was first discovered in the United States. Zlatica Hoke reports.

Video Why Are Gun Laws So Hard for Congress to Tackle?

Since taking office, President Barack Obama has spoken out or issued statements about 15 mass shootings. The most recent shooting, in which 10 people were killed at a community college, sparked outrage over the nation's gun laws. But changing those laws isn't as easy as many think. VOA's Carolyn Presutti reports.

Video Hungary Criticized for Handling of Refugees

Amnesty International has accused Hungary of breaking multiple international and European human rights laws in its handling of the refugee crisis. As Henry Ridgwell reports, thousands of migrants and refugees continue to travel through the Balkans to Hungary every day.

Video Iraqi-Kurdish Teachers Vow to Continue Protest

Sixteen people were injured when police used tear gas and rubber bullets to disperse teachers and other public employees who took to the streets in Iraq’s Kurdish north, demanding their salaries from the Kurdish Regional Government (KRG). VOA’s Dilshad Anwar, in Sulaimaniya, caught up with protesting teachers who say they have not been paid for three months. Parke Brewer narrates his report.

Video Syrian Village Community Faces Double Displacement in Lebanon

Driven by war from their village in southwestern Syria, a group of families found shelter in Lebanon, resettling en masse in a half-built university to form one of the biggest settlements of its kind in Lebanon. Three years later, however, they now face being kicked out and dispersed in a country where finding shelter as a refugee can be especially tough. John Owens has more for VOA from the city of Saida, also known as Sidon.

Video Bat Colony: Unusual Tourist Attraction in Texas

The action hero Batman might be everyone’s favorite but real bats hardly get that kind of adoration. Put more than a million of these creatures of the night together and it only evokes images of horror. Sarah Zaman visited the largest urban bat colony in North America to see just how well bat and human get along with each other.

Video Device Shows Promise of Stopping Motion Sickness

It’s a sickening feeling — the dizziness, nausea and vomiting that comes with motion sickness. But a device now being developed could stop motion sickness by suppressing certain signals in the brain. VOA’s Deborah Block reports.

Video Making a Mint

While apples, corn, and cranberries top the list of fall produce in the US, it’s also the time to harvest gum, candy, and toothpaste—or at least the oil that makes them minty fresh. Erika Celeste reports from South Bend, Indiana on the mint harvest.

Video Activists Decry Lagos Slum Demolition

Acting on a court order, authorities in Nigeria demolished a slum last month in the commercial capital, Lagos. But human rights activists say the order was illegal, and the community was razed to make way for a government housing project. Chris Stein has more from Lagos.

Video TPP Agreed, But Faces Stiff Opposition

President Barack Obama promoted the Trans-Pacific Partnership on Tuesday, one day after 12 Pacific Rim nations reached the free trade deal in Atlanta. The controversial pact that would involve about 40 percent of global trade still needs approval by lawmakers in respective countries. Zlatica Hoke reports Obama is facing strong opposition to the deal, including from members of his own party.

Video Ukranian Artist Portrays Putin in an Unusual Way

As Russian President Vladimir Putin was addressing the United Nations in New York last month, he was also being featured in an art exhibition in Washington. It’s not a flattering exhibit. It’s done by a Ukrainian artist in a unique medium. And its creator says it’s not only a work of art - it’s a political statement. VOA’s Tetiana Kharchenko has more.

VOA Blogs