How The Oral Polio Vaccine Can Cause Polio

One of the vaccines used to prevent polio has actually been causing some people to get the disease.

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SCOTT SIMON, HOST:

Just last month, the World Health Organization announced that two of three strains of polio had been eradicated. It's been one of the great success stories of modern medicine. The disease, which, of course, can lead to paralysis, has been reduced to just a handful of cases around the world. But now scientists say there's been a troubling setback. One of the vaccines used to prevent polio has actually been causing some people to get polio.

NPR's Jason Beaubien joins us now. Jason, thanks for being with us.

JASON BEAUBIEN, BYLINE: Hey. Good morning.

SIMON: I understand the problem begins with what's called a live vaccine, which has little bits of weakened polio virus in it, given to children around the world. What seems to have gone wrong?

BEAUBIEN: Yeah, that is the crux of it - that this - the oral polio vaccine that's used primarily in low- and middle-income countries - it's been the workhorse of this global effort to eradicate polio. But it is a live vaccine. It's cheap. It's easy to administer.

However, this live vaccine is continued to be used worldwide. And while you're doing that, some of that vaccine has gotten out into the world. And it's mutated. It starts circulating again, just like regular polio. But early on, it's just - it's still a vaccine. It's not dangerous. And then slowly, it sort of regains strength. And they're finding they can actually genetically see this - that scientists can actually trace it back directly to the vaccine. And now these vaccine-linked cases are actually causing more cases of paralysis each year than actual traditional - what scientists call wild polio.

SIMON: Now, we should underscore, Jason, this is not the version of the vaccine that's given to youngsters in the United States.

SIMON: Why are other countries still using it?

BEAUBIEN: Right. So in the United States and in Europe and other countries like that, it - we're using an injectable vaccine, which is a dead vaccine. It is not a live virus, and it cannot cause polio. So that should not at all be a concern. The issue, however, is that it's an injection that has to be given. It's given four times between the ages of 2 months and 7 years. So just administering it is difficult.

And just frankly, there is not enough global stockpile of that vaccine to vaccinate all of the children around the world, you know, four times over the course of their childhood. So there's some real problems with that. That, ultimately, would be the goal - is to eventually get to the point where you're not using oral polio vaccine, but it's not logistically possible at this point.

SIMON: You learned this week the Centers for Disease Control takes this problem so seriously they're actually sending dozens of experts to these countries affected. What do they plan to do?

BEAUBIEN: Yeah. They're calling it the surge. And they're going to be deploying between 75 and 100 extra staff from the CDC out primarily into Africa to try to just address these vaccine-derived outbreaks and just clamp them down as soon as they can because the idea is that if you can stop them then you will stop that virus from continuing to spread and really try to strengthen these systems so that they can get control of this and hopefully, you know, get rid of this other source of polio at a time when they're tantalizingly close to actually wiping out the disease.

SIMON: NPR's Jason Beaubien, thanks so much.

BEAUBIEN: You're welcome.

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