Polio is an infectious disease caused by a virus. Most people have no symptoms, but 1% suffer permanent paralysis, weakness, or death. The Inactivated Polio Vaccine (IPV) nearly eradicated polio in the U.S.
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Table of Contents for Polio
How do you get polio?
How many people get polio every year?
What are the symptoms of polio?
How soon do symptoms appear?
What are complications of polio?
How is polio treated?
How effective is the polio vaccine?
What is the immunization schedule for polio?
What are polio vaccine names?
Polio, or poliomyelitis, is a crippling infection that is caused by a virus called poliovirus. Polio can cause lifelong paralysis and death.
Polio is very contagious. The polio virus spreads when the stool (feces) of an infected person or the droplets from their sneezes or coughs get into the mouth of another person. Polio is contagious before symptoms appear and up to 1-2 weeks afterward.
There have been no cases of polio in the United States for more than 30 years, but the disease still occurs in parts of Asia and Africa where vaccines are not routinely given to children.
Before the vaccine was introduced in the mid-1950s, polio epidemics were common in the United States and between 13,000-20,000 were paralyzed per year.
Around 95% of people with polio do not have any symptoms at all. Up to 24% of people with polio will have flu-like symptoms for 2-5 days that go away on their own, such as:
- Sore throat
Around 1-2% of polio cases result in non-paralytic viral meningitis, an infection of the covering around the brain and spinal cord. Meningitis causes neck stiffness, fever, headache, nausea, and other symptoms.
Less than 1% of people develop paralytic polio, or “flaccid paralysis,” in which the patient is left with permanent muscle weakness or an inability to move the legs, arms, or both. It can cause death if it paralyzes the muscles that are necessary for breathing. Of people with paralytic polio, 2-5% of children die and up to 30% of adults die.
The incubation period for polio is usually 6-20 days, but it ranges from 3-35 days.
About 1% of people with polio develop weakness or paralysis. Even children who seem to have recovered can develop new muscle pain, weakness, or paralysis 30-40 years later as adults. This is called Post-Polio Syndrome (PPS). Severe cases of polio can also be deadly.
There is no cure for polio. Treatments focus on relieving symptoms while the immune system naturally clears the virus from the body.
The first polio vaccine was an inactivated injectable vaccine that was created in 1955 by Dr. Jonas Salk. It was followed by a live attenuated (weakened) oral vaccine that was created in 1961 by Dr. Albert Sabin. The use of these vaccines has nearly eradicated polio worldwide.
The injectable polio vaccine (IPV) is the one that is currently used in the United States. The oral polio vaccine (OPV) is no longer used in the U.S., but it is still used by other countries where polio is common because it is better at stopping the spread of polio virus to others.
The change to an all-IPV immunization schedule in the U.S. in 2000 was because the few cases of polio that were occurring (8-10 cases per year out of 2.4 million doses) were caused by the OPV vaccine itself and not “wild” polio virus.
One dose of the polio vaccine provides almost zero immunity, but three or four doses on the proper schedule are at least 99% effective.
Doctors recommend that children get four doses of the polio vaccine (IPV) for the best protection, with one dose given at each of the following ages:
- 2 months
- 4 months
- Between 6 months and 18 months old
- Between 4 years and 6 years old
The polio vaccine is very safe. The inactivated polio vaccine (IPV) can’t cause paralytic polio because it only contains killed viruses.
The risk depends on the vaccine, but the single IPV vaccine (Ipol®) commonly causes the following side effects:
- Local reactions where the shot was injected (redness, swelling, tenderness)
- Loss of appetite
- Persistent crying
Polio vaccines sometimes cause a severe allergic reaction called anaphylaxis within 4 hours. The risk is estimated to be less than one in a million doses of the IPV vaccine.
Shoulder Injury Related to Vaccine Administration (SIRVA) occurs when the vaccine needle accidentally punctures the bursa, ligaments, or tendons. It can cause permanent shoulder weakness and pain.
There have been reports of Guillain-Barre Syndrome (GBS), a condition that causes severe muscle weakness or paralysis. It is unknown if the polio vaccine can cause GBS.
There have also been reports of children who developed seizures as a result of very high fevers after receiving the polio vaccine. This rare but severe side effect is also known as a febrile seizure.