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Polio childhood vaccine rates have dropped in the US: What parents should know

Childhood vaccination rates have declined from pre-pandemic levels. After a case of polio was detected in New York, here's what parents need to know to keep kids safe.
/ Source: TODAY

After the U.S. recorded its first polio case since 2013 this summer, what was once perceived by many Americans as a disease of the past has become a more present threat.

In July, the New York State Department of Health confirmed a case of paralytic polio in Rockland County. Weeks later, on Aug. 12, New York health officials reported that poliovirus had been detected in wastewater samples from New York City, “suggesting likely local circulation of the virus,” according to a NYSDOH press release.

Polio, or poliomyelitis, is a potentially disabling and deadly disease caused by the poliovirus, which is highly infectious and can infect the spinal cord, leading to paralysis, per the U.S. Centers for Disease Control and Prevention.

In late 1940s, polio was disabling 35,000 people in the U.S. every year, according to the CDC, but thanks to vaccination, wild polio has been eliminated in the country since 1979.

Although polio has been under control for decades in the U.S., this recent case demonstrates that it’s still a threat, especially for unvaccinated people. Amid a backdrop of declining childhood vaccination rates around the country, what do parents need to know and how can they keep their kids safe?

What does this recent case of polio mean? 

“It was a very concerning event for a number of reasons, the first of which is the health of the individual. … Paralytic polio is a terrible thing, but it also sets off public health alarm bells because paralytic polio is a reasonably rare outcome of poliovirus infection,” Dr. Adam J. Ratner, director of the Division of Pediatric Infectious Diseases at Hassenfeld Children’s Hospital at NYU Langone, told TODAY. 

Less than 1% of people who get infected with poliovirus will go on to develop paralysis, Ratner added, so there could be hundreds more cases for this one that led to paralysis.

“While it’s possible that there was only a single infection and that person happened to get super unlucky … (what’s) much more likely is that it was an indicator of ongoing spread (of poliovirus) in the community,” said Ratner.

According to the CDC, it's unclear how the individual became infected with polio, a sign of community transmission.

Most people who become infected with polio will not become sick; about 1 in 4 will experience flu-like symptoms that go away on their own, and a small number will develop severe complications, such as meningitis (a swelling of the membranes protecting the brain and spinal cord) or paralysis, per the CDC.

Another cause for concern is that the polio vaccination rates among young children in certain zip codes of Rockland County, where the paralytic case was found, are as low as 37%, NBC News reported

According to the CDC, only 60.3% of children under the age of 2 in Rockland County had received three doses of the polio vaccine by August 2022. Comparatively, the current childhood vaccination rate for polio across the U.S. is about 93%, according to the CDC.

“The combination of knowing that there is virulent poliovirus circulating in the community and the childhood vaccination rates against polio are so low make it very worrisome that we’re going to see more cases of paralytic polio,” Ratner said.

The polio-stricken individual in New York was unvaccinated and tested positive for vaccine-derived poliovirus type 2, a strain related to the weakened virus in the oral polio vaccine, per the CDC.

What does "vaccine-derived polio" mean? There are two kinds of polio vaccines, explained Ratner: the inactivated polio vaccine, or IPV — which came out in 1955 and is what everyone in the U.S. gets now — and the oral polio vaccine, or OPV, which has not been used in the U.S. since 2000 but is still used in other parts of the world. The IPV protects against wild poliovirus and vaccine-derived poliovirus, according to the CDC.

“Some types of oral polio vaccine, because they contain live, weakened virus, in very rare cases, can cause so-called vaccine-derived polio in under immunized populations,” Nina Schwalbe, adjunct assistant professor at the Mailman School of Public Health at Columbia University, told TODAY.

When a person receives the oral polio vaccine, they can shed the virus in their feces, explained Schwalbe. “What happened over time was that (shedded) virus essentially shifted and changed … into forms that in very rare instances are strong enough to actually cause polio in people that are not immunized," she added.

The case in New York "indicates a chain of transmission within the United States originating with a person who received a type 2-containing oral polio vaccine (OPV) abroad," per the CDC, and this strain spread to the unvaccinated individual in Rockland County.

If you're fully vaccinated, you are protected against all strains of polio, including the vaccine-derived ones, the experts stressed. 

The primary series of the IPV is three doses given at 2 months old, 4 months old and between 6 through 18 months old, and then another booster dose that kids get prior to school entry (between 4 to 6 years old) — so four doses total, per the CDC.

“The polio vaccine series that we give in the United States (IPV) is well over 99% protective against paralytic polio,” said Ratner. But the childhood vaccination rates for polio and other diseases have been dropping, the experts noted. For example, global coverage with three doses of the polio and DTP vaccines was 86% from 2010 to 2019, but it dropped to 83% in 2020, according to a CDC study. About 3 million babies missed the infant vaccination series in 2020.

Why are vaccination rates dropping?

“Globally, immunization rates have dropped dramatically due to lack of access to public health services during the pandemic,” said Schwalbe. Earlier this year, the United Nations estimated 25 million children around the world had missed routine vaccinations due to COVID.

Immunization campaigns around the world were delayed or canceled as COVID-19 overwhelmed health systems, and more than two years later, we’re still making up for lost ground, the experts noted. In the U.S., many children missed out on routine services, including immunizations, because health services were harder to access during COVID and various lockdowns, said Schwalbe.

“That has absolutely contributed to under-vaccination, as has a doubling down on (vaccine) hesitancy,” Schwalbe said. Vaccine hesitancy and misinformation is not new, but it has been amplified by the COVID-19 pandemic and threatens the response to future pandemics, NBC News reported.

All 50 states and the District of Columbia have laws that require children entering public school or day care to get certain vaccinations, including the polio vaccine, according to the CDC.

These state laws requiring polio vaccines for children often also apply to private schools, but not always, and some states allow non-medical or religious exemptions, which tend to cluster geographically, increasing the risk of an outbreak in those communities, according to the CDC.

Despite state laws and school vaccine mandates, children still fall through the cracks, the experts noted. "School mandates are excellent, but they’re only applicable when you go to school and right now ... we need to focus immediately on getting all children vaccinated," Schwalbe said.

As the CDC has noted, the greatest risk of polio circulating is to unvaccinated individuals.

What does the vaccination rate in my community mean for my family?

Low vaccination rates in a community can create more opportunity for a disease to spread. But the experts stressed that regardless of the vaccination rate in your area — whether it's high or low — the best thing you can do to protect your family is to make sure you're all up to date on all your vaccinations, especially polio.

For parents looking for information on vaccination rates — perhaps you have a child too young to be fully vaccinated against polio or other diseases and therefore is at higher risk — state-level data about vaccination rates is released yearly by the CDC. The CDC’s VaxView website provides data on vaccine coverage for all ages across the U.S., including maps that break down rates by state. There is a site for each age group: ChildVaxView for kids 0 to 35 months, SchoolVaxView for those entering kindergarten, TeenVaxView for 13 to 17-year-olds, and AdultVaxView for people 18 and up. 

“Many public health departments, either state or local, put out data at a finer resolution,” said Ratner. The NYSDOH, for example, breaks down polio vaccination coverage by county on their website.

The New York City Department of Health and Mental Hygiene also published a zip code-level map of the polio vaccination rates, said Ratner, which shows steep differences between neighborhoods. “There are a bunch (of zip codes) that are more than 99% and then you have these pockets where it’s under 70%,” he added.

Zip-code level data polio vaccination rates may not be available for other cities or states, Ratner said, but your local health department is good place to start looking. Both experts stressed the importance of having good data on vaccination coverage.

“The statistics and surveillance that we have are a tool for public health officials to understand where we have access issues, where we have equity issues, and then focus and target our interventions on the people that vaccines are not reaching,” said Schwalbe.

What should you do if you’re worried about vaccination coverage in your area?

“The primary thing that parents can do to protect their kids is to get their kids vaccinated … regardless of what the rate is in the neighborhood,” said Ratner, adding that all family members should be vaccinated against polio, as well.

Polio spreads from person to person, per the CDC, and the virus enters the mouth through contact with feces of an infected person — for example, you pick up minute pieces of feces on your hand and touch your mouth or you consume contaminated food or water. It can also spread through respiratory droplets, which is less common. Good hygiene (with soap and water, as hand sanitizer doesn't kill polio) can help to reduce transmission, but vaccination is the most effective strategy, the CDC noted.

Kids who are fully vaccinated (four doses of IPV) are protected, said Ratner, so parents do not need to take any additional precautions. "If we were seeing many more cases, public health departments might think about whether there are things other than vaccination to be done, but I don't think we're at that point," he added.

The IPV is safe for immunocompromised people, per the CDC, but those who are severely immunocompromised might not respond as well to the IPV as someone with an intact immune system, Ratner noted.

“What I would say to the parents of an immunocompromised child is to have a discussion with their pediatrician," he added, because the IPV may still provide some protection.

This is another reason why everyone should get vaccinated against polio and other diseases, said Ratner, because it provides "a cocoon of immunity" around vulnerable people.

“Everyone in the U.S. and around the world needs to be vaccinated against polio,” added Schwalbe. “We have the ability to protect every child, everywhere from a debilitating and potentially deadly disease."