Polio is back in the U.S. Here’s how to stay safe

UUntil recently, polio was a historic site in the United States Once a scourge that paralyzes or kills tens of thousands of children each year, the United States declared the disease officially eradicated in the United States. 1979, thanks to widespread vaccination.

But polio has returned. On July 21, New York State Department of Health announced a case of polio in an unvaccinated man in Rockland County. Poliovirus has been found in wastewater in both Rockland and neighboring Orange County, as well as in New York City.

The development has led to legitimate alarm. A group of researchers write in a report published August 16 in Weekly report on morbidity and mortality. The bottom line is that anyone who has not been fully vaccinated should update their shots immediately. Here’s what to know about what a resurgence of polio in the US means for your health.

A brief history of recent polio

As recently as 1988, polio was a worldwide threat: circulating in 125 countries and causing an average of 350,000 cases of paralysis or death each year, according to the World Health Organization (WHO). That was the year that the World Health Assembly was founded Global Polio Eradication Initiative with the goal of eradicating this disease, like smallpox has been officially eradicated in 1980.

The means to end polio are the same as for smallpox: worldwide vaccination. The strategy worked very well. Today, polio is endemic in only two countries – Afghanistan and Pakistan – so far there have been only 18 cases between them this year, according to the Initiative. But there are problems with that overall success story, and they have to do with the vaccination campaign itself.

What is vaccine-derived polio?

There are two types of polio vaccine: oral polio vaccine (OPV), as the name implies, given by mouth; and inactivated polio vaccine (IPV), given by injection. IPV uses destroyed poliovirus to familiarize the immune system with the disease and initiate a response if it encounters a live virus. OPV uses a attenuated virus — so weakened that it can do the same job as the immune system bait without actually causing the disease.

The major advantage of OPV is that it is much cheaper and easier to use, making it the vaccine of choice for mass vaccination campaigns. The disadvantage is that in extremely rare cases, attenuated virus can return to virulence, infecting the recipient of the drops, or allowing the revived virus to be shed in the feces of an infected person and remain in the body. in wastewater – leading to the possibility of so-called vaccine-derived polio in others.

Virulence reversal is very rare. Since 1988, an estimated 18 million cases of polio have been prevented by vaccination and 1.5 million lives have been saved. based on US Centers for Disease Control and Prevention (CDC). Since 2000, UNICEF report, 10 billion doses of OPV have been used worldwide. Measured against those numbers, vaccine-derived polio is low-risk, with a total of 540 global cases so far this year—Excluding the US case — and a recent peak year happen in 2020, when 1,100 cases were reported globally. Usually, there are fewer cases in a given year.

To eliminate the domestic problem, the US stopped using OPV in 2000 and switched to IPV exclusively. But that doesn’t prevent vaccine-derived strains from being imported by travelers from abroad, or by a U.S. resident traveling internationally, who received the virus from someone who received the virus. OPV and bring it home. Typing of the virus found in the Rockland County man showed that it was indeed a vaccine-derived strain that caused the disease.

No matter how the virus got here, it’s within us now — and not necessarily limited to water supplies in just three New York areas. If one tourist can bring it into one state, other travelers can take it anywhere.

“The fact that we found it in wastewater tells you that it’s more common than people appreciate,” said Ian Lipkin, professor of epidemiology at Columbia University’s Mailman School of Public Health. “We’re looking at the tip of the iceberg.”

More to virologist Vincent Racaniello of Columbia University School of Medicine: “I suspect it has been in a lot of places in the United States. In fact, I think if we look at every major city in the United States, we’ll find vaccine-derived polio in definitely sewage. “

Scary low polio vaccination rate

Vaccine guidelines call for children to receive three doses of polio vaccine before the age of two to be considered fully immunized. However, the use of polio vaccine in the United States is low. In Rockland County, just over 60% Eligible children received three doses. (These rates vary widely within the county; in one zip code, only 37% of children were vaccinated by Aug. report.) In Orange County, less than 59% of children are fully immunized. In New York City, the rate is much higher, about eighty six%, but the average varies by county, with Manhattan reaching 91% and Brooklyn following the other counties at 81%. The statewide vaccination rate is just under 79%.

Nationally, the figure is higher, with 92.6% of children being fully immunized before the age of two, According to CDC. But here, too, there are local differences; For example, only 79.5% of children in Oklahoma, along with 80.3% in South Carolina, are fully immunized. That worries experts because every unvaccinated child is at risk of becoming a polio victim – and a reservoir for the virus. For every case of polio, up to 200 other people are likely to be infected people who have no signs of the virus or who have mild cold or flu-like symptoms. Each one of them is a walking propagation vector.

“The vast majority of people infected with polio have no symptoms,” says Lipkin. “They don’t even know they’re infected, but they can spread the disease.”

Even people who have been immunized with IPV — the only polio vaccine used in the United States — may be able to clear the virus. OPV establishes what is known as intestinal immunity, which means that — assuming a person is not among the few in whom the poliovirus returns to a virulent state — there is no viral replication in the intestinal system, and therefore no infectious virus is shed in the feces. But IPV, because it must be injected to be effective, does not provide enteral immunity, which means that if a person vaccinated with IPV chooses a vaccine-derived virus strain, that active virus can reproduce in the intestines and are excreted.

It doesn’t pose a health risk to someone who gets IPV, but they could unknowingly contribute to the spread of the virus if they come into contact with it. “You won’t develop polio” if you have the IPV vaccine, says Racaniello, “because once the virus enters your bloodstream, your immune system takes care of it. “But the virus can reproduce in your gut and you can shed it and it could end up in the sewage that way.”

What can you do to reduce your risk?

The reappearance of polio does not necessarily mean that a nationwide epidemic is imminent. But it’s a wake-up call that unvaccinated children and adults must get vaccinated now. “The solution to the problem is just to make sure you’re vaccinated,” says Racaniello. “Because if you get vaccinated, you won’t get polio.”

But the COVID-19 pandemic has shown that the wisdom of immunizing a contagious disease can work against politics, claims of individual liberties, and baseless rumors about safety and effectiveness. of injections. Even before the pandemic, there was a Strong anti-vaccination community in the United States, and that cohort hasn’t disappeared. “There are all sorts of bizarre conspiracy theories put forward by one group or another,” says Lipkin. “That’s a big deal.”

The good news is that both polio vaccines are remarkably effective and long-lasting. If people received a full course of the vaccine as children, they do not need a booster shot now. “Anyone who has had a complete polio vaccine does not need a booster shot,” says Racaniello. “Immunity to vaccination-induced polio will last a lifetime.” This is true whether you received IPV or OPV in childhood, he stresses.

That’s not to say that polio boosters are never needed. People traveling to high-risk areas, like Afghanistan, Pakistan or any country with high rates of vaccine-induced polio – such as Nigeria, where there are 238 out of 540 cases worldwide demand this year — should get a boost first, says Lipkin.

For most people, however, the re-emergence of the polio virus in the United States poses no danger, thanks to the simple prevention of a vaccine. They beat the disease once before in the US, and now that they can work across the country, they can do so again.

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Write letter for Jeffrey Kluger at [email protected].

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