Zika Vaccines Ready for Testing, While Yellow Fever Shots Fall Short

IRA FLATOW: This is Science Friday. I’m Ira Flatow. The Zika virus is now active in over 50 countries around the world. And while it’s not spreading here in the US via mosquitoes yet, mosquito season is here, and nearly 1,000 travelers have already been infected and returned to the US with the virus.

But if the virus has been advanced, new vaccine candidates have been racing along, too, and a couple of them already passed animal tests. They’re ready for prime-time. We have Phase I human trials, including a sort of unusual vaccine for humans, at least– a DNA vaccine. Here to tell us how it works is Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases at NIH in Bethesda. He’s also a National Medal of Science recipient. Welcome back to Science Friday. Been a while, Doctor.

DR. ANTHONY FAUCI: Yes, good to be with you, Ira.

IRA FLATOW: So how many Zika vaccines are ready for human trial?

DR. ANTHONY FAUCI: Well, there are about a half a dozen that are at various stages of preclinical studies, as you mentioned, in in-vitro and in animal models. Some of them are federal government-driven. Some are in collaboration with industry. And some are done by industry alone.

The one that you mentioned that is very close to going into a Phase I trial, there are actually a couple of versions of the same vaccine. You mentioned DNA vaccine. Well, this is a vaccine that has actually been used in the past for a similar type of a virus, a Flavivirus called West Nile virus, which is of the same general family and genus as Zika virus is.

And what it is is a plasmid or a circular component of DNA in which you can insert a gene or genes that expresses a particular protein of the virus in question. In this case, the virus in question is Zika, and the particular protein is a particular component of the outer coating. And when you inject this into an individual, into the muscle, what it does, it codes for a protein.

And the protein takes the form of a small virus-like particle, which the body makes a very good immune response against. And we saw that in a different disease, with West Nile, but what you referred to, also correctly, was that just recently, over the past week or so, there have been reports in the medical literature of the prototype of this virus, as well as another virus that was injected into mice, and protected the mice from challenge with two different types of Zika virus.

So A, it induces a rather robust immune response. And at least in a mouse model, it protects. Now, a mouse model is not the optimal model for comparing to humans. But there are a couple of people and companies that are going into, now, the non-human primate model to do the identical types of experiments.

IRA FLATOW: Could we be having a couple of different ones that win out, and not just one winner?

DR. ANTHONY FAUCI: Oh, absolutely. I think whenever you’re dealing with a vaccine, there are so many uncertainties in vaccines that, A, you could have a few successful ones, and you want to have several in the pipeline to just cover your bets, so that in case one fails or there’s technical problems with the production of one or more, that you have a few candidates. So I think when you’re dealing with a vaccine of any type, the general rule is to always go with multiple candidates so that you really have backup, in case there’s failure. And if you have multiple successes, all the better.

IRA FLATOW: Yeah. There was news, also, about a harmless bacteria carried by bees and butterflies that might stop the spread of Zika by infecting the mosquitoes.

DR. ANTHONY FAUCI: Yeah. Yeah.

IRA FLATOW: Tell us a little bit about where that is.

DR. ANTHONY FAUCI: OK. So that’s a bacteria called Wolbachia. Wolbachia is a bacteria that can harmlessly infect a variety of insects. You’ve mentioned a couple, but it can also infect mosquitoes. And it has two components to it. It interferes with the propagation of the mosquitoes, but it also does not allow the mosquito to successfully transmit the particular pathogen in question. In this question, it would be Zika.

There have been a number of studies that were done in Australia, successfully using it in mosquitoes in Australia. And there are tests that are planned to be done under the appropriate control conditions here in the United States and in South America.

IRA FLATOW: Were you disappointed by Congress not taking up Zika virus before they went away for the weekend.

DR. ANTHONY FAUCI: More than disappointed, Ira. It was really disturbing. Because we do need the money to continue to proceed in a variety of areas. The CDC, which is very heavily involved in South America, in the Caribbean, and particularly in Puerto Rico– Puerto Rico is very vulnerable. They’re having about 1% per week of the population being infected already, and we haven’t even gotten into the peak mosquito season there, in our territory of Puerto Rico.

We, with our vaccine trials, we will start a vaccine Phase I trial at the end of August. At the latest, the beginning of September. And there are a number of other candidates that will be not too far behind that, or even at the same pace as that.

And the Phase I trial generally takes a couple of months. It’s a small trial for safety and to determine if you induce a response that you would predict would be protective. But right after that, if you want to smoothly transition into an efficacy trial, namely to determine if it works, that would likely start in the beginning of 2017, like January or so in 2017.

In order to prepare for that larger Phase II trial, we need to start preparing the sites now. And we are very rapidly running out of money, even the money that we’ve moved from other accounts to keep us going. So we’re reaching that point, both at the NIH and at the CDC, that we really need some action about appropriating this money.

IRA FLATOW: So the trials will not go on if you don’t get the money.

DR. ANTHONY FAUCI: Well, no. The Phase IIB trials, yes, yes. The Phase I, we can do with what we have. But the Phase II would likely stop short if we don’t get money, which is something we don’t want to happen. Because even though they will be initiated in the early part of 2017, we want a smooth transition from Phase I right into Phase IIB, which won’t happen if we don’t get the money.

IRA FLATOW: Wow. And you know summer’s coming up, and the mosquitoes are moving.

DR. ANTHONY FAUCI: Well, you know, right now, as you mentioned, we have about 1,000 travel-related cases in the continental United States. We have over 250 pregnant women among those cases that we have in the continental United States. And as we get into the mosquito season, particularly in the Southeastern part, in the Gulf Coast area, where we have seen pockets of outbreak of other similar viruses, like dengue and chikungunya, it’s concerning that we may have, and likely will have, localized outbreaks of Zika on the continental United States. And the thing we absolutely have to do is to prevent them from becoming sustained and from becoming disseminated.

IRA FLATOW: All right, Dr. Fauci, I want to thank you for taking time to be with us today. And good luck and a happy holiday to you. Anthony Fauci, who is director of the National Institute of Allergy and Infectious Disease at the National Institutes of Health in Bethesda, Maryland.

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