Paul Offit, MD: Hi, my name is Paul Offit. I'm talking to you today from the Vaccine Education Center at the Children's Hospital of Philadelphia. It's Friday, December 9th, 2022. Well, this summer something unusual happened in Rockland County, New York, and that is that a 27-year-old unvaccinated man was paralyzed by poliovirus.  

Now, we eliminated poliovirus from the United States by 1979. So, what's happening? And I think to understand what happened to this man, we need to go back to the beginning, which is the mid-1950s at a time when polio would paralyze 25[,000] to 30,000 children a year, would cause 1,500 children to die every year because we didn't have a vaccine. But in the middle of the 1950s, around 1955, Jonas Salk made a polio vaccine. He made it by taking the virus, growing it up in cell culture, purifying it, and then completely inactivating it with a chemical, a so-called whole killed viral vaccine. And we used that vaccine in the United States from 1955 up until 1962.  

in 1962, that vaccine was replaced by Albert Sabin's vaccine, which was a live-weakened form of the virus. We have other live-weakened viral vaccines, like the measles vaccine, or the mumps vaccine, or the German measles (or rubella vaccine), or one of the rotavirus vaccines, or the chickenpox vaccine. Those are all made the same way by taking a virus, in this case poliovirus, and there's three strains of poliovirus, strains 1, 2, and 3, and what Dr. Sabin did was he weakened those viruses, the natural viruses, the wildtype viruses, by growing them up in cell culture, in monkey cells. And that vaccine then was then used in the United States from the early 1960s up until around the year 2000, and it eliminated polio from the United States by 1979; it eliminated polio from the Western hemisphere by 1994. But unfortunately, there was a problem with that vaccine, and it wasn't trivial, and that was that in some people, and it was extremely rare, roughly 1 out of every 2.4 million people who got that vaccine would develop paralysis caused by the vaccine virus. Because the vaccine virus, which would reproduce itself in the intestine over and over again, could occasionally revert to essentially so-called neurovirulent strain or a wildtype strain. I mean, it really, it caused a clinical syndrome indistinguishable from polio. So, in other words, this was called vaccine-associated paralytic polio, and it was rare, but it was real.  

So, although we eliminated polio from the United States by 1979, throughout the 1980s, throughout the 1990s, every year, eight to 10 children would be paralyzed by that vaccine. For that reason, in the year 2000, we then eliminated the use of the oral polio vaccine. Albert Sabin's oral polio, live-attenuated viral vaccine was eliminated for use in this country in 2000. So, for 20 years now, more than 20 years, we have only used the inactivated vaccine, and that's why we then eliminated even vaccine-associated paralytic polio. But there are many countries that still use the oral polio vaccine, and for that reason, there are those viruses, those revertant viruses, those vaccine-associated paralytic polio strains, still circulate. And that's what happened to this man. What happened to this man was that he was, because he was unvaccinated, that virus, that type 2 revertant virus that was originally derived from Albert Sabin's polio, Albert Sabin's live-attenuated polio vaccine, that caused him to be paralyzed. 

Now, know this, know that only about 1 of every 2,000 people who are infected with that vaccine-derived strain will become paralyzed. So, his case of paralysis represents the tip of a much, much bigger iceberg. And you know that's true because what has happened at that point was, we looked at wastewater in Rockland County, looked at wastewater in surrounding counties, like Sullivan County, Ocean County, and found that there was this type 2 revertant virus, this vaccine-associated virus was in the wastewater, so that says that at least thousands, and possibly tens of thousands, and possibly hundreds of thousands of people could have been infected with that virus. Now, the inactivated polio vaccine, which we use in this country and have only used since the year 2000, is very good at preventing poliovirus from entering the bloodstream and traveling to the brain or spinal cord and causing harm. So, anybody who’s vaccinated with the inactivated polio vaccine will be prevented from getting polio if they are infected with this type 2 revertant strain from the vaccine. But the inactivated vaccine doesn't induce intestinal immunity. So, you could be infected with this type 2 revertant paralytic strain and shed it in your stool, and then pass it on to others. You'll never be paralyzed, and those who are vaccinated will never be paralyzed, but they can still spread the virus.  

So, I think what we need to do, what it's important to do now, is to look in the wastewater not only in New York or in Rockland County, but in Philadelphia; in Portland, Oregon; in Las Vegas, Nevada; in Los Angeles, California; in Indianapolis, Indiana, to answer the question, how prevalent is this particular strain? This neurovirulent type 2 strain that was derived from the vaccine, which you know is circulating throughout the world and may well be circulating in this country. And if we find that that's true, it just makes it all the more important to make sure that we've gotten the inactivated vaccine, which will then prevent us from being paralyzed by this virus but won't prevent us from transmitting this virus. This is an easily solved problem, just make sure everybody who's gotten the inactivated vaccine gets it. If you're an older person like me and you got the oral polio vaccine … you got the inactivated vaccine in the '50s and then the oral vaccine in the 1960s, or if you got the oral polio vaccine from the 1960s up till the year 2000, you are protected against this virus, but you're not protected if you're not vaccinated. So, we need to make sure that everybody's vaccinated and we're going to learn, I think, over the next few months or year just how common this particular type two revertant strain is in this country.  

Thank you.