No polio scholar knew more than Albert Sabin, a scientist at the Polish-American University in Cincinnati, whose vaccine against the crippling disease had been in use around the world since 1959.

Sabin’s oral vaccine provides lifelong immunity. There was a downside to this, which Sabin, who died in 1993, refused to acknowledge: In rare cases, the weakened live polio virus in the vaccine could mutate, reactivate the virus, and cause polio.

These rare mutations—one of which appears to have paralyzed a young man in Rockland County, New York, a member of the Hasidic Jewish community that resists vaccination, according to official reports—have taken center stage in the global campaign to eradicate polio, the largest international public health effort in history.

When the World Health Organization (WHO)-led campaign began in 1988, the goal was to make the world polio-free by the year 2000.

By 2015, polio was almost completely eradicated everywhere except Pakistan and Afghanistan. But by 2020, cases were reported in 34 countries, mainly in sub-Saharan Africa and Asia.

Although numbers have declined over the past 18 months, some cases have emerged in Ukraine and Israel; In June, the polio virus was detected in the sewers of London, and now north of New York City, the first in the United States since 1993.

But the nature of the polio threat has changed. “Natural” or “wild” polio now only occurs in a few war-torn areas of Pakistan and Afghanistan, where gunmen have killed dozens of officers vaccinating locals against polio.

Almost everywhere else in the world, by contrast, vaccine components are derived from mutations of weakened viruses. Sabin designed the vaccine virus to infect the human gut without making it sick, but in rare cases, the virus mutates in the gut.

In this case, it goes in like a lamb but comes out like a lion, capable of crippling vulnerable people who pick up the virus as a result of poor hygiene, after coming into contact with objects such as diapers or bath towels that contain traces of the feces of an infected person. the person

There are three types of polio virus. Type 2, the version that causes almost all vaccine-related cases of polio, paralyzes only about 1 in 1,000 people infected. Others may not get sick at all or have simple viral symptoms, such as a runny nose or diarrhea.

Rockland County officials say her polio case may have been contracted in the United States, but the virus must have originated in a country, usually Asia or Africa, where the oral vaccine is still administered. In the United States, since 2000, doctors have given a different vaccine, developed by Dr. Jonas Salk in 1955, that contains killed or inactivated poliovirus.

Because polio infection rarely results in paralysis, the Rockland County case suggests that other people in the community are carrying the virus. County Health Department spokeswoman Beth Cefalu said exactly how many are being investigated.

If the patient acquired the virus in the United States, “it would suggest that at least in that area there may be substantial transmission,” said Dr. Walter Orenstein, an Emory University professor who led the national immunization program from 1988 to 2004. The pressure is on the Centers for Disease Control and Prevention (CDC) to find the best way to stop these chains of infection, he added.

As of Friday, July 29, county health officials set up inactive polio vaccine clinics and sent 3,000 letters to parents of county children whose routine immunizations, including polio, were not up to date.

However, although the Salk vaccine prevents paralysis and is highly effective in protecting a community from infection, in situations where polio is widespread, a person vaccinated with this vaccine can still carry polio germs in their intestines and spread it to other people.

Depending on the number of infected people in the community, the CDC may consider using a new live vaccine product, known as new oral polio vaccine 2 or nOPV2, which is less likely to mutate into a virus, he explained. Orenstein.

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

To complicate matters, vaccine virus polio outbreaks increased, mainly in sub-Saharan Africa, when world health leaders announced that type 2 poliovirus had been eradicated from the wild and that this type of virus had been eradicated. Vaccine virus.

Unfortunately, mutant forms of type 2 that arose in 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. Anand Banerjee, leader of the Bill & Melinda Gates Foundation’s polio program, the mutant virus is still circulating in some areas where the new vaccine has not yet begun to be used.

The likelihood of a major outbreak linked to the Rockland County case appears slim. Dr David Hayman, professor of epidemiology at the London School of Hygiene and Tropical Medicine and former director of the global polio eradication effort, said the virus could spread widely in areas with low vaccination coverage and poor polio surveillance. .

Rockland County has extensive experience fighting vaccine-preventable outbreaks. In 2018 and 2019, he tackled a measles epidemic among the community of anti-vaccine Hasidic rabbis that resulted in 312 cases.

“Our people have beaten measles and I’m confident we’ll eliminate the new health problem,” County Commissioner Ed Daly said at a news conference Thursday.

Scientists believe polio can be eradicated from the entire world by 2026, Banerjee said, at a cost of $4.8 billion. Much of that money has yet to be collected from donor countries and charities.

And he added that the polio case in the United States provides a reminder that “polio potentially travels on a plane while the virus still exists in some corners of the world.”

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