Dr. Petri Dishes on Polio

By Reuvain Borchardt

Dr. William Petri, chair of the World Health Organization’s Polio Research Committee, discusses the recent discovery of polio in a person in the New York City suburb of Rockland County, as well as in wastewater in New York City. Dr. Petri is vice chair of the Department of Medicine at the University of Virginia, where he is also a professor of Medicine, Pathology, and Microbiology. He spoke with Hamodia by phone from Bangladesh, where he Is conducting research into polio and testing new polio vaccines, in projects funded by the National Institutes of Health and the Gates Foundation.

Polio was recently discovered in wastewater in New York City. But thus far have there been any human cases confirmed besides the one in Rockland County?

No, there haven’t.

What happened with the unfortunate man who got paralytic polio — it was like an airplane crashing. Three different things had to go wrong.

The first was that an international traveler who had received the live vaccine — the “Sabin vaccine,” which we don’t use in the U.S. anymore — traveled to New York, introduced it, and it spread fecally-orally. The vaccine is excreted in the stool for three weeks. So that was the first thing that went wrong — someone introduced the Sabin vaccine virus into New York.

When you say it was spread fecally-orally, does that mean like somebody might use the bathroom, not wash their hands properly, then touch something which has oral contact with someone else?

Exactly. People who are vaccinated with this live-virus vaccine excrete the virus in their stool for about two to three weeks. And that’s what happened in New York.

So the person who had excreted it had just received the vaccine in another country during the last few weeks.

Yes, it was someone who had been vaccinated probably within the last three weeks maximum, then traveled to New York, and transmission was established in New York, as you said, by not washing hands after going to the bathroom. Any surface that’s contaminated is a potential mechanism for spread.

Then, the second factor that went wrong is that the vaccine virus mutated so that it can cause paralysis again, which is a rare occurrence.

The third bad thing that happened was, the person who contracted paralytic polio had not been vaccinated as a child.

All those three things had to happen for the U.S. to get its first case of paralytic polio in years.

The good news is that even though we don’t use this live virus vaccine anymore, we do immunize children in the U.S. with the inactivated “Salk” polio vaccine. Every child has four doses of that vaccine before they start school, and that’s the reason we’re not seeing more cases of paralysis, even though the virus has been identified in sewage in three different locations in the New York City metropolitan area.

So you’re saying this person had received this vaccine — which is not given anymore in the United States — outside the United States, and within three weeks, came to the United States and excreted it, infecting someone via fecal-oral contamination. But anybody who received that vaccine — which
used to be given in the U.S. — decades ago is safe, and the people around them are safe, and they nothing to worry about?

That’s right. So if you got your childhood immunizations, you’re protected against paralytic polio.

Even if you got that live vaccine decades ago.

That’s correct.

If you were vaccinated before 1970, you received both the Sabin and the Salk vaccines, and so you’re doubly protected.

The reason this live-virus Sabin vaccine is used is that it gives immunity against being infected with polio. The Salk vaccine that we give in the U.S. right now protects you from getting paralyzed, but it doesn’t protect you from getting infected and passing the infection on to other people. That’s the reason that we’re probably seeing this vaccine-derived polio virus in several different locations in the sewage in the New York area — because most people who live there are not immune to being infected, because they never got the Sabin vaccine; they were born after 1971. They only got the Salk vaccine.

And so we may see a continued presence of the vaccine virus in New York City for some time, just because most people are not immune to being infected with polio and passing it fecally-orally from one person to another.

Are there any places in America, other than New York, in which polio was found in the wastewater?

Only in the metropolitan New York area, in like three different sewage distribution systems.

I don’t know how many communities are actually testing for this. It might be present in other cities as well, because, again, most of the people in the U.S. are not immune from being infected, they’re just immune from having paralytic polio.

Does finding polio in the wastewater mean that there are more people who actually have polio? Or can it just mean that there are more people who have recently been vaccinated and excreting it during the few weeks after vaccination?

We don’t use in the U.S. anymore the Sabin vaccine, which is excreted. So, finding polio in different wastewater systems means there’s two possibilities. Possibility number one is that this is the same virus that caused paralytic polio, and it’s spreading into three different parts of the metropolitan area. Possibility number two is there are three different international travelers who got the Sabin vaccine. There’s no way to tell between those two possibilities without sequencing the virus. I don’t know that they’ve done that yet.

I don’t know if the person in Rockland, who excreted the virus that affected someone else, also visited New York City. Is it possible that this wastewater is all from this one person? Or does it seem inevitable that more people either contracted the virus or recently traveled internationally and got the Sabin vaccine and are excreting the virus?

I think it’s likely that the virus has spread from that initial person who developed paralytic polio. But, again, that can be determined by sequencing the virus, because the sequence is unique for each virus. If three different sewage distribution systems have the same sequence, that suggests that there is a circulating vaccine-derived polio virus in the metropolitan area.

Polio has just about been eradicated. Do they generally test for polio in the wastewater? Or are they only doing it now because of this case?

I doubt that it’s part of the routine stuff that they do in New York City; it’s probably more in response to this case. But I don’t know.

This is a relatively new development, doing environmental surveillance for polio viruses by sampling wastewater. It’s a really great way to know if there’s any virus in your community. If you tap into one sewage line, you’re testing like 100,000 people upstream. It’s a very, very powerful way of doing surveillance.

Polio seems very scary; everyone has seen the old pictures of the kids in iron lungs, and people who have suffered paralysis. But not everyone’s affected the same way. What are the typical symptoms of polio? Are there people who catch it but are asymptomatic? And what percentage of people might suffer paralysis?

In populations of people who have not been vaccinated, there are at least 100 people who get infected for each person who develops paralysis. It’s not unlike what we saw with COVID — many people got asymptomatic or mild infection; few, tragically, end up in the hospital or die.

Wild polio — as opposed to vaccine-derived polio — has almost been eradicated from the world. There have been 20 cases of wild polio paralysis in the last year, and that’s down from hundreds of thousands of children who used to be paralyzed every year. That’s thanks in part to this campaign that I’m involved in called the Global Polio Eradication Initiative. It’s supported by the WHO, the CDC, the Gates Foundation and the Rotary Club.

The wild polio virus is endemic in Pakistan and Afghanistan. It was reintroduced into Africa about six to eight months ago. It’s in Malawi and Mozambique; there have been four cases there. There’s a big vaccination campaign going on to prevent it from spreading elsewhere in Africa, because Africa has been free of wild polio for about seven years now.

If someone is vaccinated, whether it’s with the Sabin vaccine or the Salk vaccine, how protected should they feel?

It’s not 100%, but it’s in the high 90s.

If you were traveling to Pakistan, Afghanistan or Africa, and you had not received a polio booster as an adult, I would recommend that you get one. That’s the one situation where we boost adults.

This wastewater monitoring will be very helpful in helping public health authorities decide whether to recommend that adults get a booster or not. It may well be that this will just peter out and they’ll stop detecting it. Or maybe they’ll detect it in other locations.

Also, detection is quantitative. You can tell how much polio virus is present. If it’s going down, then maybe it doesn’t make sense to ask adults to get boosted. But if it’s increasing, maybe another decision is reached.

If someone gets the Sabin vaccine, they’re at a small risk of excreting the virus which another, typically unvaccinated, person can then catch. But is the person who got the vaccine at risk also?

The person who got the vaccine is not at risk, because the vaccine provides a protective immune response both against them getting further infections and being paralyzed. But family or community members of the person who got the vaccine are at risk, but only if the virus mutates to a paralytic form. It can mutate in the person who got vaccinated. And so, when he or she excretes the virus and other people are exposed to that mutated virus, it now causes paralysis. Or maybe it gets passed between three or four people before it finally mutates to cause paralysis.

Again, this was an extraordinarily rare event.

So the person himself who gets the Sabin vaccine is not at any more risk than someone who got the Salk vaccine.

That’s correct.

The reason that we stopped using the live virus vaccine in the U.S. in 1971 was that we no longer needed it, because we had eradicated polio in the U.S.; and because of this very, very rare side effect that happens one out of a million people. But if you don’t need to use the vaccine that is causing a one-in-a-million side effect, you don’t use it.

So, all the millions of people in the United States who might have gotten the live vaccine decades ago have no reason to worry?

That’s right. And everyone since 1971 got the Salk vaccine. And so they likely do not need to be concerned about it, either, because they’re protected against being paralyzed.

The only unknown is if we got to the point where there’s high levels of circulating vaccine-derived polio virus in the U.S., whether we would go to recommending that adults get their one booster if they’ve not already been boosted.

Since polio has virtually been eradicated, are our public health systems and doctors equipped to deal with polio patients? If we do start seeing more polio infections, is there a medical infrastructure in place to deal with that?

Yes, I think so.

The biggest problem with polio is that it uncommonly can paralyze your diaphragm. That’s why people were in iron lungs, which are like primitive ventilators. Iron lungs only exist in museums right now. We actually have one in our museum at the University of Virginia.

Maybe one of the good things from COVID is that we’re replete with ventilators. So if we had a big outbreak of polio — which will not happen because we’re a highly vaccinated population — we would have the ventilators to support them.

Can people take a test to check their immunity level to polio?

Not easily. We do know what immune response is associated with protection from polio, and it’s called a “serum neutralizing antibody response reaction.” You take the serum from the vaccinated person and you look in our laboratory to see, can it neutralize the polio virus, but that’s a very, very specialized assay. It’s quite time consuming and requires use of the wild polio virus which we keep safely contained in only a few labs around the world. In the U.S., it’s really only done in Atlanta by the CDC.

They can’t really start mass-testing everyone for polio immunity. Rather, if you’ve been boosted once as an adult, you can be sure there’s nothing more to be done. If you’ve been vaccinated as a child after 1971, you’re protected against paralytic polio. Paralysis is the only thing you worry about with polio.

Do you personally have any investments or financial stake, or stand to benefit financially in any way, from vaccines?

No, I don’t. I have no conflicts of interest from a financial standpoint. None of my investments are going to benefit, and I’m not a consultant.

If the health authorities tomorrow said that everybody must get a polio booster, you would not benefit one penny from that in any way?

That’s correct.

But I don’t think the public health authorities will recommend that all adults receive a polio booster. The only thing that would make them do that is if they begin to see that the amount of polio virus in the wastewater is increasing, either in the number of places they’re finding it, or in the amount of virus. Without that, I don’t think that they’ll make that recommendation.

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rborchardt@hamodia.com