How delays in vaccination could lead to a resurgence of polio

Most American parents rarely think about polio beyond the moment their children are immunized against the disease. But there was a time in this country when polio paralyzed 20,000 people in one year, killing many of them.

Vaccines have turned the tide against the virus. Over the past decade, there has been only one case in the United States, related to international travel.

This could change very quickly if polio vaccination rates decline or access to the vaccine becomes less difficult.

Robert F. Kennedy Jr., a longtime vaccine skeptic who might become Secretary of Health and Human Services, said the idea that vaccination has all but eliminated polio is a “myth.”

While Mr. Kennedy has said he does not plan to keep vaccines away from Americans, he has long maintained that they are not as safe and effective as claimed.

In 2023, he said, batches of an early version of the polio vaccine, contaminated with a virus, caused cancer “that killed many, many, many more people than polio ever killed.” The pollution was real, but the research A link to cancer has never been proven.

Aaron Seery, an attorney and advisor to Mr. Kennedy, represented a client seeking to challenge the approval or distribution of certain polio vaccines on the grounds that they may be unsafe.

These efforts seem unlikely to succeed. There is widespread support for vaccination among prominent Republicans, including President-elect Donald J. Trump and Senator Mitch McConnell, who contracted polio as a child.

But the Secretary of Health and Human Services has the authority to discourage vaccination in less direct ways. He or she can withdraw federal funds for it Child vaccination programmeshastening the end of school mandates in the states already Lack of inclination towards vaccines Or increases doubts about the shots, exacerbating a Low immunization rates.

Scientists say that if polio vaccination rates decline, the virus could slip into pockets of the country where large numbers of people are not vaccinated, leading to chaos again. The virus may have been nearly eradicated in its original form, but its resurgence remains a persistent threat.

Any decision the Trump administration makes on a polio vaccine is likely to resonate around the world, said Dr. David Heyman, an infectious diseases physician at the London School of Hygiene and Tropical Medicine and a former polio eradication leader at the World Health Organization.

He added: “If the United States withdraws the license, many other countries will do the same.” A resurgence of polio that is so close to being eradicated “would be very sad.”

Before 1955, when the vaccine was introduced, polio affected more than 15,000 Americans each year and hundreds of thousands worldwide. In 1952 alone, the disease killed 3,000 Americans after paralysis left them unable to breathe.

Many of those who survived are still living with the consequences.

“People really underestimate how terrible polio is,” said Dr. Karen Kowalski, a physician and polio specialist at the University of Texas Southwestern Medical Center in Dallas.

Many of those who have recovered now suffer from “post-polio syndrome”: some of the original symptoms return, including muscle weakness and respiratory problems.

Dr. Kowalski cares for about 100 post-polio patients who require braces, wheelchairs or other devices to cope with progressive weakness. Some of them are elderly people who were infected before the vaccine was available; Others are middle-aged immigrants from countries where polio has been a problem much longer than in the United States.

For some survivors, the idea of ​​polio returning is unfathomable.

Carol Polk became ill in 1943, when she was three years old. Her right leg never recovered, and throughout her life she walked with a pronounced limp and suffered from almost constant pain.

Ms. Polk is among the luckiest. Until recently, she did not have the breathing, swallowing or digestive problems that often plague polio survivors.

She lived a “wonderful, wonderful life” with a husband and three daughters, earned a law degree and traveled abroad extensively.

But always, everywhere, she’s calculating how far away the next seat is, how long she can hold out, and whether a particular activity is worth the debilitating pain the next day.

She did not participate in the 1963 March on Washington or exercise, as she so desperately wanted, or go hiking, skiing, and biking with her husband.

If there were a public hearing on the polio vaccine now, “I would go, take my brace off, let them see my leg and ask them: ‘Is this what they want for their kids?'” she said.

Polio now incapacitates far fewer children. Vaccination has successfully eliminated the virus from most parts of the planet, reducing the number of cases by more than 99.9 percent and preventing an estimated 20 million cases of paralysis.

However, the virus has turned out to be a stubborn enemy, and its eradication has been repeatedly set back.

In 2024, 20 countries reported cases of polio, and the virus was detected in wastewater in five European countries, decades after it was officially eliminated from the region. In Australia.

“Any decrease in coverage rates increases the risk of polio infection anywhere,” said Oliver Rosenbauer, spokesman for the World Health Organization’s polio eradication programme.

There are three types of polio viruses, and eradication requires the disappearance of all three types. For many years, the goal has been tantalizingly close.

Type 2 was declared defeated in 2015, and Type 3 in 2019. Type 1 is now only widespread in Afghanistan and Pakistan. In 2021, the two countries together had just five cases; In 2024, they have 93.

But these numbers tell only part of the story. In a surprising development, an oral vaccine used in some parts of the world has succeeded in maintaining the spread of the polio virus long after it became extinct.

In most low- and middle-income countries, health officials still rely on the oral vaccine, which is given as two drops on the tongue. It is inexpensive, easy to administer, and prevents transmission of the virus.

But they contain a weakened virus that vaccinated children can shed into the environment through their stool. When there are enough unvaccinated children to transmit the infection, the pathogen slowly spreads, regains its virulence and eventually causes paralysis.

The problem is this: Since 2016, the oral vaccine used for routine immunization has not provided protection against type 2 virus. Global health authorities made a deliberate decision to reformulate the vaccine based on the disappearance of the naturally occurring type 2 virus.

Which It turned out to be premature. More type 2 viruses have been shed by children who were orally vaccinated in some parts of the world than officials expected. When some unvaccinated children, or those given the newer oral vaccine, encountered this type 2 “vaccine-derived” virus, they became infected and paralyzed.

The vaccine-derived polio virus now causes paralysis in more children than the natural virus. For example, Nigeria eliminated all so-called wild-type polio in 2020. But in 2024, the country saw 93 cases of CVDPV, more than a third of the global total.

None of this poses a problem for Americans — as long as they are vaccinated.

Inactivated polio vaccine (IPV) used for routine immunization of American children protects against all three types of polio. These formulations contain dead virus and therefore cannot cause illness or revert to a dangerous form.

But like some other vaccines for infectious diseases, it does not completely prevent infection or transmission of the virus. This aspect is Among the criticisms leveled at Mr. SerryCounselor to Mr. Kennedy.

However, experts said that was less important than the vaccines’ almost perfect power in preventing paralysis.

“Yes, yes, it’s true, IPV does not prevent transmission,” said Dr. William Petrie, an infectious disease physician and former chair of the World Health Organization’s Polio Research Committee. “But boy, this is the best thing since sliced ​​bread at preventing paralysis.”

However, it means that people who have been vaccinated against IPV can keep spreading the virus, even when they themselves are protected against the disease and paralysis.

So here’s the real-life scenario that worries researchers: A person vaccinated with the oral polio vaccine in another country might bring the virus to the United States and then shed it in its weakened form. This has already happened in other countries.

As long as most of the population remains vaccinated, it is unlikely to lead to an epidemic. But if the virus makes its way into communities with low vaccination rates, it could spread, then revert to a virulent form that can cause paralysis.

This is what happened in New York in 2022, when polio struck an unvaccinated 20-year-old man from an ultra-Orthodox Jewish community in Rockland County.

The vaccination rate in that county was just over 60 percent, compared to the national rate of 93 percent.

The virus that paralyzed the young man had been spreading for months, and was later discovered in wastewater in several New York counties, where vaccination rates reached about 60 percent, prompting the state to take urgent action. Declare a state of emergency.

Genetically related polio viruses have been detected in wastewater samples in Britain, Israel and Canada, indicating widespread transmission of the disease. Authorities later found two distinct types of vaccine-derived poliovirus type 2 in New York wastewater, suggesting two separate importations.

If polio re-emerges in the United States, it is unlikely to be as dire as it was in the pre-vaccine decades. Many elderly people still remember that when they were children, they were not allowed to swim in rivers or swimming pools, or anywhere the virus might lurk.

“The reason we weren’t allowed to play in the rivers in the 1950s was because untreated sewage was dumped into the rivers,” Dr. Heyman said.

He added that this is no longer the case, so “there will not be widespread transmission immediately in the United States.”

But even if a few children were paralyzed, “it would be terrible.”