WASHINGTON—Forget mosquito bites. Volunteers let researchers in the United States inject them with the dengue virus in the name of science—and an experimental vaccine protected them. Next up, scientists plan to use this same strategy against dengue’s cousin, the Zika virus.
It’s called a human challenge, a little-known but increasing type of research where healthy people agree to be deliberately infected in the quest for new or improved vaccines against a variety of health threats, from flu to malaria. Wednesday’s dengue study offered more evidence that what sounds bizarre not only can be done safely, it can offer important clues for how well a shot might work.
“What we’re trying to do is accelerate vaccine research,” said senior author Dr. Anna Durbin of Johns Hopkins University’s school of public health. It may be the best way “to know if you have a stinker before you try to test it in thousands or tens of thousands of people.”
The dengue candidate proved highly promising, researchers reported in the journal Science Translational Medicine.
Dengue fever may have slipped from the headlines as the related Zika virus sweeps through Latin America, but every year mosquito-borne dengue causes devastating outbreaks throughout the tropics and subtropics. While most people survive dengue with few or even no symptoms, more than 2 million a year suffer serious illness and about 25,000 die.
Creating a vaccine has been tough. It must work against four separate strains of dengue, and a shot that’s only partially protective might backfire. That’s because people who survive one type of dengue can suffer worse symptoms if they’re later infected with another strain.
What about Zika, the dengue relative that’s been linked to babies born with unusually small heads? Already, researchers are planning similar challenge studies that could start even before there’s a vaccine candidate, Durbin said.
“We see a Zika challenge model as really beneficial for not only vaccine development but also to learn more about Zika itself,” she explained. “We know very little about Zika right now,” including how long it stays in blood and other parts of the body.
Key to these challenge studies: Scientists must modify a virus strain in the laboratory so that it doesn’t make volunteers openly ill but still is strong enough to spark a mild infection, what Dr. Stepehen Whitehead of the National Institutes of Health’s National Institute of Allergy and Infectious Diseases, who led the vaccine development, called “that perfect in-between.” Plus, that mimics what happens with both dengue and Zika, where most people who become infected never report symptoms. AP