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How to Make a Zika Vaccine in the Middle of an Epidemic

If you’ve never made a vaccine from scratch before, this is how it’s done.

As cooler weather descends on the United States, the fear surrounding a local spread of Zika has started to die off. The Wynwood neighborhood in Miami, the area hit hardest by local transmission of the virus in the US this summer, was officially declared Zika-free in September, and the mosquitoes that carry the disease will be even less common as the temperature dips.

But the current outbreak—which can cause birth defects in babies—emerged in Brazil, where it's about to be summer. The mosquito population grows in heat and rain, making a second wave of Zika cases possible in parts of South America. That's why researchers are scrambling to develop a vaccine that could protect the most vulnerable.


Col. Nelson Michael is a medical doctor and a researcher who is currently part of a team of scientists developing a Zika vaccine at the Walter Reed Army Institute of Research. Another vaccine candidate, developed by the National Institutes of Health, started human clinical trials in August, and Michael told me the WRAIR vaccine will be doing the same come Halloween. I called him up to find out how exactly one goes about making a vaccine in the middle of an epidemic, and whether there are better ways of preparing for and preventing outbreaks in the future.

Motherboard: To start, can you give me a layman's terms walkthrough on how you go about creating a vaccine? I mean in explain-like-I'm-five terms.
Col. Nelson Michael: The first thing you'd like to know is how do people who get infected with the pathogen—be it bacteria or fungus, just a 'bug'—how does their immune system normally fight it off? And if you understand how that works, then the pathway is to say: of the ways that we traditionally make vaccines—there's lots of different recipes to do that—how can we mimic what the human body does normally to fight off this disease?

Which recipe did you end up using for Zika?
We took a virus, grew it up, and we killed it with formaldehyde—just like Jonas Salk did in 1952 for polio. That protected mice, it protected non-human primates or monkeys, and sometime around Halloween we'll start the first injections of that in humans.


Col. Michael speaks to foreign dignitaries during a recent visit at WRAIR. Image: WRAIR

When will we know if it's safe and effective for people?
Working as fast as we can, we will have the first idea as to whether or not the vaccine is going to work probably by summer of next year. Which, by the way, is unbelievably fast. Usually from concept to having a vaccine that's ready for public health distribution it's 10 years, and $1 billion.

Why is it so much faster in this case?
This is not the first rodeo when it comes to these types of viruses, called flaviviruses [which includes Zika]. Dengue is a great example. Just now, Sanofi Pasteur is licensing a dengue vaccine. There's a licensed vaccine for yellow fever. So we have a really, really strong track record in making vaccines against that type of virus.

I know most vaccines are not 100 percent effective. For something like Zika, how effective would it need to be to continue development?
It depends who you ask, but the actual percent efficacy is something that is negotiated up front with national regulatory authorities—in our country that's the FDA—and the manufacturer. The numbers people are talking about for this particular disease are in the range of 70 percent.

"We [need to] see it coming, like a tornado warning two hours before it hits your town. That saves lives."

How does that compare to other vaccine efficacy?
The typical benchmark is usually not much less than 70 percent, but for a disease like HIV, even if it was 50 percent, people would enthusiastically embrace it. That's why there's no easy answer. The HPV vaccine is 100 percent, but that's pretty unusual.

Is this process, of scrambling to create a vaccine after an outbreak has emerged, the best method? Are there other things we could do?
The kind of thing we're doing now is reemphasizing the fact that we need to have surveillance sites for infectious diseases that are much more sentinel. By that I mean we see it coming, kind of like a tornado warning two hours before it hits your town. That saves lives.

The US government is increasingly investing in surveillance networks in parts of the world that diseases are continually emerging from. And there are molecular techniques that allow us to identify pathogens we haven't seen before. So both technology and building networks are something we're all doing right now.

This interview has been edited for length and clarity.

Correction: An earlier version of this story stated the Wynwood neighborhood of Miami was the only area in the US where local transmission occurred. There are a few other areas of Florida where local transmission was detected.