New York State reported Thursday that it has detected a case of vaccine-derived polio in a person in Rockland County, north of New York City, the first such recorded case in the United States since 2013.
In a statement, the state department of health said the person, who was not identified, was infected with a type 2 vaccine-derived poliovirus, which would have come from oral polio vaccine used in a number of countries, but not the United States. The U.S. stopped using oral polio vaccine in 2000.
The statement did not give details of the individual’s age or whether he or she had recently traveled outside the country.
Kimberly Thompson, a polio expert who is president of the non-profit organization Kid Risk, said it’s not a surprise to see a vaccine-derived case pop up in this country, noting public health authorities in the United Kingdom recently discovered vaccine-derived polioviruses in sewage in London, indicating some transmission there.
“With Covid having disrupted immunization (even in the U.S.) and travel now having resumed and much more type 2 poliovirus transmission happening … it’s been only a matter of time before we’d have some detection of polioviruses in sewage, as happened recently in the U.K, or more tragically, a case,” Thompson told STAT in an email. “There’s just a lot more polio going around than there should be.”
The oral vaccine contains live but weakened polioviruses, which immunized children excrete in their stools. In places where hygiene is poor, these viruses can spread from child to child, immunizing others as they do. But as they spread, the vaccine viruses can regain the power to paralyze. Such cases are called vaccine- derived polio.
The United States uses injectable polio vaccine that contains killed viruses to teach the immune system to recognize and fight off polio. It cannot cause paralysis.
Mary Bassett, New York State’s health commissioner, said people who are vaccinated against polio do not face a risk from the newly discovered case. But children who are not immunized against the virus should receive the vaccine.
“Based on what we know about this case, and polio in general, the Department of Health strongly recommends that unvaccinated individuals get vaccinated or boosted with the FDA-approved IPV polio vaccine as soon as possible,” Bassett said.
Rockland County will host vaccine clinics on Friday and Monday, the department’s statement said.
The last recorded case of vaccine-derived polio in the United States was in a young, unvaccinated child in Minnesota. The child had not traveled outside the country and it was unclear how she contracted the vaccine viruses that paralyzed her.
The last case of polio caused by wild polio viruses in this country occurred in 1979.
Walter Orenstein, a polio expert from Emory University, said detecting where the virus in the New York case came from is critical.
“It would be important to genetically sequence the virus and see if it can be linked to the many [vaccine-derived polio] outbreaks, particularly in Africa and Asia,” he said via email.
The world has been trying to eradicate polio for decades, with two of the original three types of polio — types 2 and 3 — having been driven out of existence. But the remaining version, type 1, has defied efforts to end its spread to date.
Wild-type polio cases are at low numbers; the viruses are only endemic at this point in Afghanistan and Pakistan, which have recorded a total of 12 cases this year. But recently it was discovered that viruses from Pakistan had made their way to Malawi and Mozambique, a highly unwelcome development.
Meanwhile, the numbers of vaccine-derived cases have exploded in Africa and some other parts of the world after the failure of an effort in 2016 to take type 2 viruses out of the oral vaccine.
It was felt that given the fact that wild type 2 viruses no longer existed, it was not ethical to use oral vaccine containing type 2 viruses, because of the risk they would regain the power to paralyze.
In a coordinated move called “the switch,” countries around the world were told to stop using trivalent oral vaccine — vaccine that contained all three types of polioviruses — and begin to use a bivalent form that did not include type 2. In the years since, chains of transmission of type 2 vaccine-derived virus have spread to more than 40 countries around the world and the polio eradication program has struggled to contain the spread.
So far this year 167 children in 12 countries have been paralyzed by type 2 vaccine viruses, not including the individual in New York.
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