WASHINGTON—Wanted: Volunteers willing to be infected with the Zika virus for science.
It may sound bizarre, but researchers are planning just such a study — this winter, when mosquitoes aren’t biting — to help speed development of much-needed Zika vaccines.
The quest for a vaccine began less than a year ago as Brazil’s massive outbreak revealed that Zika, once dismissed as a nuisance virus, can harm a fetus’ brain if a woman is infected during pregnancy.
Now, researchers in the United States have begun safety testing of two vaccine candidates, and more experimental shots are poised to enter that preliminary testing soon. Any that seem promising will have to be tested in thousands of people in parts of Latin America and the Caribbean that are hard-hit by the mosquito-borne virus — the only way to prove if an experimental vaccine really protects.
Even if all goes well, a vaccine wouldn’t be available for general use any time soon.
But a different kind of research also can offer clues for vaccine development. It’s called a human challenge study, when healthy — and nonpregnant — people agree to be injected deliberately with a virus, mimicking natural infection while scientists track how their bodies react.
The first question is even more basic: How much of the virus does it take to infect someone?
If government regulators agree, researchers could find out by injecting paid volunteers with different amounts of lab-grown Zika virus as early as December in a Baltimore hospital. That information will help the researchers later, when they’re ready to test an experimental Zika vaccine.
“We’re looking at these human challenge protocols not only as an important step in vaccine development but as a means to learn more about Zika,” said Dr. Anna Durbin of Johns Hopkins Bloomberg School of Public Health, who is leading the work. “We can look at things that you just can’t do in someone who’s naturally infected.”
Some questions and answers about the development of Zika vaccines:
Q: Which potential vaccines are first in line?
A: Two so-called DNA vaccines have begun preliminary safety testing, one made by the National Institutes of Health and the other by Pennsylvania-based Inovio Pharmaceuticals.
They mark a new kind of technology. Traditionally, vaccines are made using a dead or weakened virus to train the body’s immune system to recognize that infection and fight it off. DNA vaccines may be easier to make. Scientists used a circular piece of DNA, called a “plasmid,” to carry genes that prompt the body itself to produce certain Zika virus proteins, alerting the immune system.
That piece of trickery worked in animals. The phase 1 studies in dozens of people will check for safety, and whether the vaccinations rev up human immunity enough to justify further tests.
Q: What else is in the pipeline?
A: “We are right now in a race of time to get the best vaccine,” said Dr. Anthony Fauci, director of NIH’s National Institute of Allergy and Infectious Diseases.
Multiple candidates are important as there’s no way to predict which kind will work best. The DNA vaccines simply were ready for human testing first.
In October, safety tests are set to begin using the more traditional killed-virus vaccine, developed by the Walter Reed Army Institute of Research.
The NIH also is developing a vaccine using live-but-weakened virus, the type thought to trigger particularly long-lasting immune protection. That’s the kind used to protect against rubella, which back in the 1960s caused an epidemic of birth defects.
