What to Know About Polio: Vaccines, Symptoms and How It Spreads

Even after someone recovers from polio, they can develop muscle pain, weakness or paralysis 15 to 40 years later. Children who recover from polio may experience post-polio syndrome as adults, with muscle weakness, fatigue, and joint pain setting in decades after their initial infection. It’s not clear why only some people develop post-polio syndrome, but those who experienced severe polio cases may be more susceptible.

How is polio spread?

Polio is very contagious. It spreads from person to person — typically, when someone is in contact with the feces of an infected person and then touches their mouth. This is particularly concerning for children under 5, who, Dr. Esper said, may struggle with hand hygiene. “Every adult who has children knows that’s how germs are spread,” he said. Less commonly, polio can be spread when droplets from an infected person sneezing or coughing enter someone’s mouth.

And as with Covid-19, it is possible to spread the virus even if you don’t have symptoms.

The oral polio vaccine, which helped the United States eliminate polio and is not administered in the country anymore, contains weakened live poliovirus. It is safe and effective, but in very rare cases, the weakened virus from the vaccine can revert to a form that can cause paralysis in other people. This is primarily a concern for unvaccinated people, whom the vaccine-derived virus can spread to, and immunocompromised people, who may have not developed immunity from the vaccine. In exceptionally rare cases — about one per every 2.4 million doses of the oral vaccine — the weakened live virus can cause paralysis in the person who received the vaccine, said Dr. Paul Offit, a vaccine expert at Children’s Hospital of Philadelphia. But the chief worry is that the vaccine virus can circulate and spread throughout under-immunized communities.

Health officials in New York confirmed that the person in Rockland County was exposed to someone who received the oral polio vaccine, which mutated to a pathogenic form of the virus. The oral polio vaccine has not been administered in the United States since 2000. Today, the polio vaccine in the United States is a highly effective shot, which does not contain live virus, unlike the oral vaccine.

There are many countries that still use the oral vaccine. “We’re always at risk of having that vaccine-derived strain come into this country,” Dr. Offit said.

How do you protect against polio?

Vaccination is the best way to guard against polio, and the highly effective vaccine is part of a regular childhood immunization schedule in the United States.