Rafael de la Barrera reaches into a freezer and pulls out a plastic jug of rusty-red liquid. He wipes frost off the label: “Zika Virus - Puerto Rico strain. 24Mar16.” The liquid—stored at -80 degrees F to keep the malicious virus inert—is a solution isolated from monkey liver cells. If the US Army pulls off this ambitious research effort, it’ll be one of the ingredients in a vaccine for the microcephaly-causing disease sweeping through the Americas.

Barrera, a lab supervisor at the Walter Reed Army Institute of Research in Silver Spring, Md., has a personal stake in this work. He’s a native of Colombia, where Zika has been ravaging much of the countryside, including his hometown. “I have family members who are infected,” Barrera says. “This is one of the reasons why we spend hours and hours working on this.”

Barrera and his team of about 10 scientists and technicians have been working full-time on Zika for the past six months. “It’s the virus du jour,” he jokes.

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So why is this Army research lab working on Zika when 15 other academic or government labs are doing the same thing? Soldiers, Marines and sailors aren’t like business travelers. They can’t telecommute or come home if they get sick. They have to be ready to go anywhere, anytime. And they get a lot of vaccinations.

Plus, the Pentagon announced this month that 17 servicemembers and family were infected with Zika while stationed overseas. That number is likely to rise. “We have to be in the game to make sure that what ultimately gets put on the shelf can be used by our folks,” said Col. Stephen Thomas, an infectious disease physician and the Zika program lead at WRAIR. “There are all sorts of nuances of that population and the mission and what they need to be protected.”

Zika isn’t fatal, and the military is made up of generally young, healthy individuals. But it still presents a threat to personnel stationed in places where the disease is widespread. That’s South America, Puerto Rico and, this summer, the southern United States. With 13 percent of Zika-infected pregnant women giving birth to children with congenital problems, “you are going to see hundreds if not thousands of kids that need lifelong care,” Thomas says.

The place where that bottle of Zika is stored is the Pilot Bioproduction Facility. If it’s the Army’s Zika greenhouse, then the chief gardener is Kenneth Eckles, who has been working on vaccines at WRAIR since 1965. “I’m not as old as the building,” he says with a laugh.

Outside the clean room sit boxes of Clorox bleach, still the best way to clean up biohazard spills. Inside the biosafety hazard level two room, negative air pressure keeps contaminants out. Without a spacesuit, gloves and respirator, I’m not allowed in. I watch through a big window.

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The Zika vaccine recipe is 140 pages long, each step laden with safety protocols, back-ups, and safety checks. The idea is to grow lots and lots of the virus in something that it likes—which is where the monkey cells come in. “You let the virus do what it does, which is infect the cells,” Eckles says.

Then the researchers “kill” the virus (viruses aren’t really alive in the first place, so scientists prefer the term “inactivate”). Next steps: Isolate virus particles, inject them into lab animals, and see if the animal’s immune system responds and builds resistance to the virus attack.

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Rapidly Deploying Vaccines

The scientist whose name adorns the big sign on the building, Walter Reed, was an army doctor who in the 1890s figured out that mosquitoes were spreading yellow fever to workers digging the Panama Canal and civilians living in marshy Washington, DC. Reed developed a vaccine, and since then, Reed’s disease-fighting legacy has continued. Today, the military maintains one of the biggest, smartest and most robust communicable disease-fighting labs in the country. Before Zika came along, there was Japanese encephalitis, dengue, chikungunya and West Nile.

Today WRAIR operates research labs in Thailand, Kenya, Uganda, Indonesia, Georgia, and other far-flung locations where researchers check for virus outbreaks. As the US military footprint around the world grows, so too does the exposure of soldiers to infectious emerging diseases. “We are a rapidly deploying force,” Thomas says. “We need things that can be given in a relatively short period of time.”

To mash the accelerator down on a Zika vaccine, Walter Reed scientists are using a manufacturing technology with a proven track record—the “dead virus” method that worked for Japanese encephalitis. So far, initial results from early stage clinical trials with collaborators at Harvard University and Beth Israel Deaconess Medical Center in Boston are “very encouraging,” says Thomas.

Once the team publishes its results, they’ll start the next stage of testing the vaccine in primate animal models. Phase I safety trials in human volunteers could be underway as soon as this fall. They’ll miss this summer’s Zika season, but with luck they might be ready for the next.