In July, public-health officials confirmed the first case of polio in New York State in close to a decade. The infected individual is 20 years old and was unvaccinated for polio, contrary to New York’s recommended childhood vaccine schedule and school requirements (with certain medical exemptions).
Officials say the patient seems to have been infected with a vaccine-derived strain of polio, which means they were likely infected by someone who received an oral vaccine (via mouth drops) abroad (the U.S. retired oral vaccines in 2000, and currently administers them through injection). The oral vaccine uses an active (albeit weakened) virus, whereas the injection uses inactive virus; this means that people who receive the oral vaccine can occasionally infect unvaccinated individuals.
Within a few weeks of identifying this case, polio was also found in New York City wastewater, which suggests there is “likely local circulation of the virus,” according to the New York City Department of Health and Mental Hygiene. This — combined with the ongoing monkeypox epidemic and COVID-19 pandemic — has left some New York residents worried about yet another outbreak, but public-health experts say vaccinated people aren’t at risk. Here’s what we know so far.
Do I need a polio vaccine?
Though it’s wise to double-check with a parent, guardian, or health-care provider, if you’re an adult, it’s very likely you were vaccinated for polio as a child, says Adam Ratner, the director of pediatric infectious diseases at NYU Langone Health. “We’ve had polio vaccines in the U.S. since the mid-1950s,” he explains. “Essentially, all adults in the U.S. now were vaccinated against polio as kids.” Because polio vaccines have been required for school entry for decades, says Ratner, he has very little concern for most American adults.
Of more pressing concern, experts say, are unvaccinated children. “There are some pockets in the U.S. and in New York State where the vaccination rate is barely above 60 percent for kids,” says Bernard Camins, the medical director for infection prevention at the Mount Sinai Health System. Unvaccinated children rely on a highly vaccinated population in order to not get sick, but as numbers of unvaccinated individuals increase, so too does the risk of infection, because the virus has greater opportunity to spread.
What are the symptoms of polio?
Most of the time, polio goes unnoticed by infected individuals, says Ratner. “About 75 precent of the time, even people who haven’t been vaccinated have no symptoms at all,” he says. “The problem is in the other 25 percent.” Even among that 25 percent, most infected persons will have mild, flu-like symptoms — fevers, headache, nausea — but some, including the individual infected in New York, will develop paralytic polio, which is irreversible.
“In a really small group — less than one percent of people — polio infections can go on to cause paralytic polio, which can lead to lifelong paralysis,” explains Ratner. “It can make it really difficult to breathe, and those are the folks that end up on iron lungs.”
Though the most severe outcome is rare, a relatively high number of people ended up contracting paralytic polio before the vaccine was developed, simply because so many more people were infected.
What does it mean that there is polio in New York City wastewater?
Because paralytic polio is a rare outcome, says Ratner, it would be highly unusual if the infected individual in New York was the only case of polio in the state. “More likely if you’re seeing that case, there are hundreds of cases going around,” he says. Still, the mere presence of polio in the wastewater isn’t particularly surprising or cause for concern among the vaccinated population. “I don’t think this is an unusual strain,” he says. “This is what happens when you have groups of people who aren’t vaccinated.”
Camins, too, urges caution when attempting to interpret the wastewater news. “It’s been found in the wastewater, but no other cases of polio have been identified,” he says. “The fact that we’re finding it in sewage water isn’t necessarily surprising, because we have a lot of people coming into the country, and that could be babies who’ve had oral polio vaccines recently.” In some cases, polio virus can mutate in young children who’ve received the oral vaccine, and can then infect unvaccinated people around them. But again, if everyone around these infants was vaccinated, says Camins, “everybody’s protected.”
What can we do to prevent polio?
Fortunately, this is an easy one: Get vaccinated.
“Polio has fallen off of people’s radar because we haven’t had it in a very long time, and that’s because we’ve been getting people vaccinated,” says Ratner. “This is what happens when our guard slips.” In other words, when we take it for granted that we’re protected from a virus because everyone else gets vaccinated, cracks in the system are likely to form. Polio prevention is achievable, thanks to highly effective vaccines, but that requires us all to get them.
“If you are a parent of a child who has not been vaccinated, it’s never too late,” says Camins. “You don’t need to rush and get them earlier than recommended, because if the mother is vaccinated, the infant has some immunity from the mother.” Still, a number of children are behind on routine vaccinations due to the COVID-19 pandemic, and it’s more important than ever to get them up to date.