What Does It Mean Now That Polio Is Back?

José R. Romero, MD

August 16, 2022

Editorial Collaboration

Medscape &

On July 14, 2022, the New York State Department of Health announced that it had identified a case of paralytic polio in a young, unvaccinated adult who had no related travel history. Even one case of paralysis caused by poliovirus is a serious event, as this is the first case of this vaccine-preventable disease in the United States since 2013.

Here are five things you should know.

Unvaccinated people are most at risk. For most of the United States, population immunity to paralytic polio is maintained through high rates of polio vaccination coverage as a result of routine infant and childhood immunization. The recent paralytic polio case occurred in an unvaccinated person who lives in a community with low vaccination rates against polio as well as other vaccine-preventable diseases. This highlights that undervaccinated and unvaccinated communities are at risk, even in the United States, where we think of polio as a long eradicated disease. Continued efforts to improve vaccination rates in undervaccinated and historically vaccine-hesitant communities are critical to keep all Americans safe from serious, debilitating, and preventable diseases like polio.

At this time, there is no change to the current Advisory Committee on Immunization Practices polio vaccination recommendations. The complete recommended polio vaccination series (three or four doses depending on age) is extremely effective in preventing paralytic polio. The case of paralytic polio occurred in an unvaccinated individual. As a clinician, you can continue to reinforce the importance of routine childhood vaccinations for all children in the United States, and of providing catch-up vaccination to unvaccinated or incompletely vaccinated children and adults.
Suspect polio. Healthcare providers should have a high suspicion for polio when seeing patients with acute flaccid weakness, especially in unvaccinated people or those with history of recent (within 30 days) international travel or exposure to international travelers. Rule out poliovirus infection in cases of unexplained acute flaccid paralysis (AFP) that are clinically compatible with polio, particularly in persons with anterior myelitis, to ensure that any case of poliovirus is quickly identified and investigated. If there is a suspicion for poliomyelitis, collect two stool specimens 24 hours apart for poliovirus confirmation. Pharyngeal specimens might also help to guide the diagnosis. It's important to send specimens as early as possible in the clinical illness to diagnose poliomyelitis. It's also important to notify your local or state health department of a suspected case.
One case of paralytic polio could mean many poliovirus infections in a community. The majority of persons infected with poliovirus, including both wild poliovirus (WPV) and vaccine-derived poliovirus (VDPV), are asymptomatic. Only 1 in 4 infected individuals present with signs and symptoms (often constitutional and/or gastrointestinal symptoms), and approximately 1 in 25 can have meningitis. Less than 1% of case patients have paralysis; once a case of paralytic polio is diagnosed, there could be many asymptomatic infections. Luckily, the recent paralytic polio case was diagnosed by a clinician and rapidly reported through our national surveillance system. It is important to pursue rapid diagnosis in persons at risk for infection and report any suspected cases for rapid testing and immediate public health response. Once again, identifying under- or unvaccinated "pockets" in your community and providing vaccine are critical to protect everyone.
Inactivated polio vaccine (IPV) does not cause polio. IPV is the only polio vaccine that has been given in the United States since 2000, and it does not contain live virus. Therefore, it cannot mutate to cause polio disease. Oral polio vaccine (OPV), which is no longer used in the United States, is a live attenuated virus vaccine that contains a weakened version of poliovirus. Vaccine-derived poliovirus (VDPV) is a strain of the weakened poliovirus that has changed over time to behave more like the wild or naturally occurring virus. This means it can infect people and cause illness, including paralysis, in people who are not vaccinated against polio. OPVs have been very effective in protecting people from polio and decreasing transmission in communities by building high population immunity; however, in underimmunized populations, the live attenuated vaccine virus can spread from person to person and mutate, changing over time into a virus that can cause paralysis. VDPVs reveal population immunity gaps — areas where not enough people have received polio vaccine.
Get your patients up-to-date on recommended vaccines. This is an opportunity to assess your patient population and strengthen vaccination coverage in your practice. It's also back-to-school season, when many children get caught up on vaccinations, and a chance to talk to adults as well. When you encounter vaccine hesitancy, remember that your recommendation remains the strongest predictor of vaccination acceptance. Addressing specific concerns of parents, sharing personal stories, and making sure that all staff convey a unified message about the importance and safety of vaccines can improve confidence in vaccines. There are resources to help you and everyone on your staff make vaccination a priority.