Is Polio coming back to America?

Why we should worry about that case in Rockland County, NY

            In June 2022, a 27-year-old man in Rockland County, New York, visited a local emergency department complaining of fever, neck stiffness, stomach pains, and leg weakness. He was hospitalized for 16 days. The diagnosis: polio. He had never left the country.

            The polio virus strain that paralyzed this man was found in wastewater in Rockland County as well as in surrounding counties. This meant that although only one person had been paralyzed, thousands had been infected. The CDC will now examine wastewater samples throughout the United States looking for evidence of this virus. They will likely find it.

            To understand what happened in Rockland County, we need to go back to the beginning.

            Polio virus enters the body through the mouth, reproduces itself in the lining of the intestine, enters the bloodstream, travels to the brain and spinal cord, and destroys cells in the nervous system causing paralysis of the arms or legs or the muscles necessary for breathing. In the 1950s, polio paralyzed as many as 50,000 people, mostly children, and killed 1,500 every year. No disease was more feared.

            In 1955, Jonas Salk made a polio vaccine. Salk took the three strains of polio virus (called types 1, 2, and 3), grew them in laboratory cells, purified them, and killed them completely with formaldehyde. The vaccine was safe and effective. But, because Salk’s vaccine was given as a shot, it didn’t induce immunity in the intestine, where polio initially reproduces itself. So, it didn’t stop the spread of polio virus. The vaccine only induced immunity in the bloodstream, which prevented polio from traveling to the brain and spinal cord. The incidence of paralysis caused by polio in the United States declined dramatically.

            A few years later, in the early 1960s, Albert Sabin had a better idea. Or at least what he thought was a better idea.

Sabin took each of the three strains of polio virus and weakened them in the laboratory. The advantage of Sabin’s vaccine was that it was cheap, easy to give (just a squirt in the mouth), and induced immunity in the intestine, which lessened transmission of the virus. By 1963, Sabin’s oral vaccine had replaced Salk’s injectable vaccine. By 1979, polio was eliminated from the United States. By 1994, polio was eliminated from the Western Hemisphere.

Progress against polio continued worldwide. In 1988, polio caused 350,000 cases of paralysis in 125 countries. In response, the World Health Organization (WHO) established the Global Polio Eradication Initiative. The results were impressive.

• In 2015, WHO certified the elimination of polio type 2.

• In 2019, WHO certified the elimination of polio type 3.

• Only polio type 1 remained. In 2022, only 30 cases of paralysis caused by naturally occurring (wild-type) polio type 1 occurred in three countries: Pakistan, Afghanistan, and Mozambique.

            But there was a catch.

By choosing Sabin’s vaccine over Salk’s, we had made a Faustian bargain. Sabin’s vaccine had a rare but real side effect. It was called Vaccine-Associated Paralytic Polio or VAPP. Sabin’s vaccine paralyzed 1 of every 3.8 million children who received it. As a result, although we had eliminated polio from the United States by 1979, we hadn’t eliminated polio caused by the polio vaccine. Every year between 1980 and 2000, about 8 to 10 children were paralyzed by Albert Sabin’s polio vaccine. For that reason, in 2000, the United States switched from Sabin’s vaccine back to Salk’s.

Why did Albert Sabin’s polio vaccine cause polio?

Although the vaccine viruses in Sabin’s vaccine were weakened, they could still reproduce in the intestines. In some people, Sabin’s vaccine virus, especially type 2, mutated in the intestine back to a strain that caused paralysis. These paralytic strains could circulate in the community, paralyzing some people who hadn’t been vaccinated, which is what happened to the man in Rockland County, who was unimmunized.

The polio strains that evolved from Sabin’s vaccine now cause more cases of polio in the world than the wild-type strains. In 2020, 1,115 cases of vaccine-derived polio type 2 were reported. In 2021, 698 cases. In 2022, another 292 cases. Eliminating polio from the world now means eliminating the polio vaccine strains that have evolved to cause paralysis.

In 2020, researchers thought they had found a better way to do this. Given that Salk’s vaccine was more expensive and harder to administer, making it difficult to use in the developing world, wouldn’t it make sense to modify Sabin’s type 2 vaccine so that it was more stable, making it less likely to evolve to a dangerous strain. Scientists created nOPV, which stands for novel oral polio vaccine type 2. The WHO approved nOPV on November 13, 2020. Since then, 590 million doses have been administered in 28 countries.

But, as Jeff Goldblum said in the movie Jurassic Park, “life finds a way.” On March 16, 2023, seven cases of paralysis caused by nOPV were reported in Burundi and the Democratic Republic of Congo. These paralytic vaccine strains have now joined the other paralytic strains caused by Sabin’s vaccine that continue to circulate throughout the world.

We will never eliminate polio until we stop administering live, weakened forms of the virus, including nOPV.

Although it is likely that the CDC will soon find that paralytic strains derived from Albert Sabin’s vaccine are still circulating in the United States, you don’t need to worry if you are vaccinated. Even if you were vaccinated decades ago. The reason that the man in Rockland County was paralyzed by a type 2 vaccine strain was that he was unimmunized and living in a relatively unimmunized community. Only 37 percent of people is his zip code were immunized against polio.

Current vaccination trends are worrisome. Recent outbreaks of measles in the United States show that vaccines have become a victim of their own success. It’s not only that we’ve largely eliminated measles from the United States; we’ve eliminated the memory of measles. The same problem applies to polio. It’s a dangerous game we play.

In 1956, I was confined to a polio ward for about 6 weeks recovering from a failed operation on my right foot. I remember polio. I remember children in iron lungs and children screaming from the hot packs placed on withered arms and legs.

This is not a disease that we want to relive.

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Beyond the Noise is written by Paul Offit, MD, an infectious diseases physician, author, FDA advisor, new grandfather, and co-inventor of the rotavirus vaccine.