No one studied polio better than Albert Sabin, the Polish-American scientist whose vaccine against the crippling disease has been in use worldwide since 1959. Sabin’s oral vaccine provides lifelong immunity. This has one drawback, which Sabin, who died in 1993, vehemently disputed: In rare cases, the weakened live poliovirus in the vaccine can mutate, reactivate the virus, and cause polio.
These rare mutations — including one that 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 been at the center of the global campaign to eradicate polio, the largest international public health effort in history.
When the World Health Organization-led campaign began in 1988, its goal was to make the world polio-free by the year 2000.
By 2015, polio 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 numbers have declined over the past 18 months, a few cases have occurred in Ukraine and Israel, poliovirus was detected in a London sewer last month and now there is a case north of New York City, the first US case since 1993.
But the nature of the polio threat has changed. “Natural” or “wild” polio has spread in several war-torn areas of Pakistan and Afghanistan, where gunmen have killed many polio vaccinators.
Almost all other cases in the world, paradoxically, originate from mutations of weakened viruses that form vaccines. Sabin designed the vaccine virus to infect the human gut without making it sick, but in rare cases the vaccine virus mutates into a dangerous form as it passes through the vaccinated person’s gut.
In this case, it goes in like a lamb but comes out like a lion, able to paralyze unprotected individuals who receive 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. .
There are three types of poliovirus. Type 2, the version that causes almost all vaccine-associated polio cases, paralyzes about 1 in 1,000 people infected. Others may not get sick at all or have simple viral symptoms like a cold or diarrhea.
Rockland County officials say their polio case may have been contracted in the United States, but the virus must have originated in a country where the oral polio vaccine is given — usually in Asia or Africa. In the United States, since 2000 doctors have administered a different vaccine, a shot, invented by Dr. Jonas Salk in 1955, that kills or inactivates the polio virus.
Given how rarely polio infection results in paralysis, the Rockland County case suggests that other people in the community are also carrying the virus. County Health Department spokeswoman Beth Cefalu said the number is under investigation. Scientists have detected poliovirus in the county’s wastewater but don’t know how many others are infected, Cefalu said in a July 26 news release.
If the patient acquired the virus in the United States, “that would suggest that at least in that area there may be substantial transmission,” said Dr. Walter Orenstein, an Emory University professor who headed the U.S. vaccination program from 1988 to 2004. He said the pressure is on the Centers for Disease Control and Prevention to find the best way to stop any chain of transmission.
As of July 22, county health officials set up inactive polio vaccine clinics and sent 3,000 letters to parents of children in the county whose routine vaccinations — including polio — were not up to date.
However, although the Salk vaccine prevents paralysis, and is very effective at protecting a community from infection, in situations where polio is widespread a Salk-vaccinated person can still carry polio germs in their intestines and spread it to others.
Depending on the number of people infected in the community, the CDC may consider introducing a new live vaccine product, known as novel oral polio vaccine type 2, or nOPV2, which is less likely to transform into a deadly form, Orenstein said.
However, the new oral vaccine is not licensed in the United States and approval under emergency authorization would require considerable bureaucratic movement, Orenstein said.
To complicate matters, outbreaks of vaccine-derived polio increased, mostly in sub-Saharan Africa, after world health leaders announced that type 2 poliovirus had been eradicated from the wild and they removed that type of virus from the vaccine. Unfortunately, mutant forms of type 2 that arose in the vaccine continued to circulate and outbreaks spread, Orenstein said. Although about 500 million doses of the new vaccine have been given, according to Dr. Anand Banerjee, leader of the Bill & Melinda Gates Foundation’s polio program, some areas with circulating mutant viruses have not yet started using the new vaccine.
The likelihood of a major outbreak tied to the Rockland County case is 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 vaccine coverage and poor polio surveillance.
Rockland County has considerable experience fighting vaccine-preventable outbreaks. In 2018 and 2019, the county battled a measles epidemic with 312 cases among followers of anti-vaccine Hasidic rabbis.
“Our people have beaten measles, and I’m confident we’ll overcome the latest health concerns,” County Executive Ed Daley said at a July 21 news conference.
Scientists think polio can be eradicated from the world by 2026, Banerjee said, but at a cost of $4.8 billion — and most of that money remains to be raised from donor countries and charities.
The US polio case provides a stark reminder, he said, that “polio could potentially be a plane ride away until the virus exists in some corner of the world.”
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