What the polio case in New York tells us about the end of polio

No one studying polio knew more than Albert Sabin, the Polish-American scientist whose vaccine against the crippling disease has been used worldwide since 1959. Sabin’s oral vaccine provides lifelong immunity. It has one drawback, which Sabin, who died in 1993, fiercely disputed: In rare cases, the weakened live poliovirus in the vaccine can mutate, regain virulence, and cause polio.

Those rare mutations – one of which appears to have paralyzed a young man in Rockland County, New York, who belongs to a vaccine-resistant Hasidic Jewish community, officials there reported July 21 – have taken center stage in the global campaign to eradicate polio, the largest international public health effort in history.

When the World Health Organization-led campaign started in 1988, its goal was to rid the world of polio by 2000.

By 2015, polio was nearly eradicated everywhere but Pakistan and Afghanistan. But by 2020, cases had been reported in 34 countries, mostly in sub-Saharan Africa and Asia. Although the numbers have declined in the past 18 months, a few cases have cropped up in Ukraine and Israel, poliovirus was detected in sewage in London last month, and now there’s the case north of New York City, the first U.S. case since 1993.

But the nature of the polio threat has shifted. “Natural” or “wild” polio circulates in only a few war-torn areas of Pakistan and Afghanistan, where gunmen have killed scores of polio vaccinators.

Nearly all the world’s other cases, paradoxically, derive from mutations in the weakened virus that constitutes the vaccine. Sabin designed the vaccine virus to infect people’s intestines without making them sick, but in rare cases the vaccine virus mutates into a dangerous form while passing through the vaccinated person’s gut.

In these instances, it goes in like a lamb but comes out like a lion, capable of paralyzing unprotected people who ingest the virus as a result of imperfect hygiene, after contact with things like diapers or bath towels that contain traces of an infected person’s feces.

Poliovirus has three types. Type 2, the version that causes nearly all vaccine-associated polio cases, paralyzes as few as 1 in 1,000 people it infects. Others might not get sick at all or have typical viral symptoms like a runny nose or diarrhea.

KHN (Kaiser Health News) is a national newsroom that produces in-depth journalism about health issues. Together with Policy Analysis and Polling, KHN is one of the three major operating programs at KFF (Kaiser Family Foundation). KFF is an endowed nonprofit organization providing information on health issues to the nation.