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Polio Making a Comeback in the US Owing to Declining Vaccination Rates

Monica Gandhi, MD, MPH

Disclosures

September 19, 2022

As a long-term infectious diseases doctor, I am dismayed at the return of vaccine-preventable diseases in the wake of the COVID-19 pandemic. The first case of paralytic polio in the United States since 2013 was reported from Rockland County, New York, on July 21, 2022, in an unvaccinated man who had recently traveled to Europe. The rate of polio vaccination in Rockland County is only 60% as of August 1, 2022, with some counties in New York reporting polio vaccination rates as low as 37% among 2-year-old children. Polio has been detected in wastewater in New York City (reported on August 12, 2022).

UNICEF and the World Health Organization have jointly reported on a massive decrease in routine childhood vaccinations during the COVID-19 pandemic response, with 25 million infants having missed out on lifesaving vaccines over the past 2 years. This backsliding in vaccination rates is due to COVID-19 related lockdowns, school closures, fear of coming to the clinic for routine care, and a loss of trust in public health.

Of course, the best way to prevent paralytic polio is vaccination. I wanted to remind you of the features of polio here and the vaccines:

Polioviruses: The poliovirus is an enterovirus — an RNA virus. The host range of polioviruses is limited to primates, which is why we are hopeful of someday eradicating this virus entirely. There are three serologic (antigenic) types, and we formerly needed to immunize against all three types, but type 2 was declared eradicated in September 2015.

Transmission and pathogenesis: Polioviruses, like all enteroviruses, are transmitted by the fecal-oral route. After replicating in the oropharynx and small intestine, especially in lymphoid tissue, the virus spreads through the bloodstream (and retrograde along nerve axons) to the central nervous system (CNS). In the CNS, poliovirus preferentially replicates in the motor neurons located in the anterior horn of the spinal cord. Subsequent death of these cells results in paralysis of the muscles controlled by those neurons.

Clinical manifestations: There are four main clinical manifestations of poliovirus infections:

  1. Most patients infected experience asymptomatic infection (90%-95%), which is a phenomenon that has been named "many called, few chosen."

  2. The second manifestation is called abortive poliomyelitis, consisting of a mild febrile illness characterized by headache, sore throat, and nausea/vomiting.

  3. The third manifestation is nonparalytic polio, which can result in an aseptic meningitis or headache with fever and neck stiffness.

  4. The fourth and most serious form of polio is paralytic polio, which manifests as a descending, asymmetric flaccid paralysis, often with painful muscle spasms. A post-polio syndrome can cause marked deterioration of the residual function of the affected muscles years later. Unfortunately, the case in Rockland County in July 2022 was one of paralytic polio.

Vaccine: There are two types of polio vaccines. One is the killed or inactivated vaccine (delivered by injection) developed by Jonas Salk, and the other is the live attenuated vaccine (delivered orally) developed by Albert Bruce Sabin. The oral vaccine should not be given to immunodeficient individuals and adults. However, the advantage to the oral vaccine is that it provides local immunity in the gut, which can protect others when excreted in the stool. The oral vaccine also generates mucosal immunity in the oral and nasal mucosa for the individual. However, very rarely, the oral live vaccine can revert to the pathogenic form (only 1 in 2.4 million doses). Given the virus's sequencing profile, this appears to be the case with the man in New York. Only inactivated polio vaccine is used in the United States, and oral polio vaccine is reserved for low-income countries when trying to protect others during a polio outbreak.

What Can We Do?

Beyond this poliovirus incident, we have seen a large outbreak of fatal measles among 700 children in Zimbabwe, with a small measles outbreak in Maricopa County, Arizona. The only way to combat these vaccine-preventable illnesses is to increase vaccination rates, which will take building back trust in public health; community involvement; and messaging on the importance of routine childhood immunizations.

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About Dr Monica Gandhi
Monica Gandhi, MD, MPH, is an infectious diseases doctor, professor of medicine, and associate chief in the Division of HIV, Infectious Diseases, and Global Medicine at the University of California, San Francisco (UCSF). She is also director of the UCSF Center for AIDS Research (CFAR) and medical director of the HIV Clinic ("Ward 86") at San Francisco General Hospital. Her research focuses on HIV and women; adherence measurement in HIV treatment and prevention; and, most recently, on how to mitigate the COVID-19 pandemic.

Connect with her on Twitter: @MonicaGandhi9

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