Medical Examiner

Searching for a Straight Shot to a Zika Vaccine

The fastest way to get a vaccine is by injecting volunteers to better learn how the disease works.

zika shot.
Not Zika. Yet.

FogStock/Vico Images/Erik Palmer/Thinkstock

Zika is coming to Maryland.

If all goes according to plan, this December, a handful of people in Baltimore will be infected with the virus. But they won’t have gotten it from traveling abroad, where most cases in the U.S. have come from. Nor will they have contracted it through sex, or from local mosquitoes.

Instead, the agent of delivery will be a needle wielded by a research assistant. Seventy volunteers will be deliberately infected with Zika so we can figure out exactly how to protect everyone else from the disease.

Deliberately giving participants an illness to allow further study of a disease is what so-called “challenge trials” are all about. “Even though they kind of freak people out,” they can be part of safe and standard research practice, and they have a long history, says Frank Miller, a former bioethicist at the National Institutes of Health who is not involved in the trial.* Over the years, they’ve been done to help speed vaccines for cholera, dengue, and other infectious diseases. And now, a team is seeking approval to conduct one for Zika, reports the Associated Press.

The trial could help us learn more about the biology of a disease that has spread quickly and dominated news coverage. Anna Durbin, an infectious disease researcher at Johns Hopkins who is leading the trial, has a lot of questions: The conventional wisdom is that only 1 out of 5 people infected even experience symptoms. Is that true? Another question is how long the virus can be sexually transmitted. Earlier this month, doctors in Rome reported that a man still had Zika in his sperm six months after his first symptoms—twice as long as the previous record.

Durbin hopes to recruit healthy participants, ages 18 to 35 or so, for her two-phase trial. In the first phase, she’ll give people a dose of the virus, then monitor participants 24 hours a day for about a week and a half while they stay in the hospital, and then for another five months or so after that (allotting to a total of six months—the amount of time that the CDC recommends that men who experience symptoms of Zika use condoms). For their troubles, participants will be given up to $200 for every day they spend under supervision in the hospital, and up to $80 for follow-up visits. This part of the trial stands to answer how long the virus stays in the body, how the disease develops, and—importantly for the next phase of the trial—how much of the virus is needed to give a vaccine a true run for its money.

The next round will test vaccines. If all goes according to plan, about 60 participants will receive vaccines this spring, and then next fall, they’ll get a dose of Zika. This will get to the important question: How will vaccines that currently show promise in the lab hold up when they’re administered to people? Challenge trials stand to speed up (and cheapen) vaccine development by weeding through candidates before they are administered to people in the real world.

In the quest to develop a very necessary vaccine, “this could be a shortcut” says Jesse Goodman, former chief scientist of the Food and Drug Administration, currently at Georgetown University. The main risk associated with Zika, of course, is microcephaly in infants born after their mothers are infected. A study published Tuesday suggested that infants born to infected moms might also experience problems in brain development, even if they don’t have microcephaly.

Microcephaly remains the largest and most damaging consequence of a Zika infection, which otherwise tends to result in fever, rash, and occasionally a headache. That means carefully managing the risks during the trial—for Durbin’s part, she’s selecting subjects who do not plan to get pregnant anytime soon, and counseling them on using condoms to protect their partners during the trial. If someone did get pregnant during the trial, the risk of microcephaly would be real. This is the cost of a challenge study. “You have to be really, really cautious about it,” says Miller. Accordingly, Durbin’s plan will undergo close ethical review before it gets the green light.

But speeding up the development of a vaccine (which will still take several years to hit the market) could change the lives of an untold number of families. For once, this instance of spreading Zika is actually a promising thing.

*Correction, Aug. 25, 2016: This article originally misstated that Frank Miller works at the NIH. He has retired. (Return.)