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

No one who studies poliomyelitis knew more than Albert Sabin, the Polish-American scientist whose vaccine against the debilitating disease has been used around the world since 1959. Sabin’s oral vaccine confers lifelong immunity. It has a downside, which Sabin, who died in 1993, fiercely disputed: In rare cases, the weakened live poliovirus in the vaccine can mutate, regain its virulence and cause poliomyelitis.

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

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

In 2015, poliomyelitis was nearly eradicated everywhere except Pakistan and Afghanistan. But by 2020, cases had been reported in 34 countries, mostly in sub-Saharan Africa and Asia. Although the numbers have fallen over the past 18 months, a few cases have emerged in Ukraine and Israel, poliovirus was detected in sewage in London last month, and now there is the case in northern New York , the first US case since 1993.

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

Almost all the other cases in the world, paradoxically, derive from mutations of 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 intestine of the vaccinated person.

In these cases, it goes in like a lamb but comes out like a lion, able to paralyze unprotected people who ingest the virus due to imperfect hygiene, after contact with things like diapers or bath towels that contain traces of feces from an infected person. .

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

Rockland County officials say their polio case may have been infected in the United States, but the virus must have originated in a country where the oral polio vaccine is still administered — usually in Asia or Africa. In the United States, since 2000, doctors have been administering a different vaccine, a vaccine invented by Dr. Jonas Salk in 1955, which contains killed or inactivated poliomyelitis viruses.

Given the rarity of polio infection leading to paralysis, the Rockland County case suggests that other people in the community may be carrying the virus. How many are under investigation, said county health department spokeswoman Beth Cefalu. Scientists have detected poliovirus in the county’s sewage but have no idea how many others are infected, Cefalu said in a July 26 news release.

If the patient contracted the virus in the United States, “that would suggest that there could be significant transmission at least in that region,” said Dr. Walter Orenstein, a professor at Emory University who led the program. vaccination from 1988 to 2004. This puts pressure on the Centers for Disease Control and Prevention to find the best way to stop any chain of infection, he said.

As of July 22, county health officials had set up inactivated polio vaccination clinics and sent 3,000 letters to parents of children in the county whose routine vaccinations — including polio — were not up to date. day.

However, although the Salk vaccine prevents paralysis and is very effective in protecting a community from infection, in situations where polio is circulating widely, a person vaccinated with Salk could still carry polio germs in their intestines and transmit to others.

Depending on how many people are infected in the community, the CDC may consider introducing a new live vaccine, known as the new type 2 oral polio vaccine, or nOPV2, which is less likely to mutate into a virulent form, a said Orenstein.

However, the new oral vaccine is not licensed in the United States and would require considerable bureaucratic movement to be approved under emergency clearance, Orenstein said.

To complicate matters further, outbreaks of vaccine-derived polio have increased, primarily in sub-Saharan Africa, after world health officials said type 2 poliovirus had been eradicated from the wild and removed this type of vaccine virus. Unfortunately, type 2 mutant forms from the vaccine continued to circulate and outbreaks multiplied, Orenstein said. Although nearly 500 million doses of the new vaccine have been administered, according to Dr. Ananda Bandyopadhyay, head of the polio program at the Bill & Melinda Gates Foundation, some regions where mutant viruses circulate have not yet started using the new vaccine.

The chances of a major outbreak linked to the Rockland County case are slim. The virus can only spread widely where there is low vaccination coverage and poor surveillance of polio cases, said Dr David Heymann, professor of epidemiology at the London School of Hygiene and Tropical Medicine and former director of the global polio eradication effort.

Rockland County has extensive experience dealing with vaccine-preventable outbreaks. In 2018 and 2019, the county battled a measles outbreak of 312 cases among followers of anti-vaccine Hasidic rabbis.

“Our people have overcome measles, and I’m sure we’ll eliminate the last health issue as well,” County Executive Ed Daly said at a July 21 news conference.

Scientists believe polio can be eradicated from the world by 2026, Bandyopadhyay said, but at a cost of $4.8 billion – and much of that remains to be raised from donor countries and charities.

The polio case in the United States offers a not-so-subtle reminder, he said, “that polio is potentially a plane ride away as long as the virus still exists in some corner of the world.”

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