The World Health Organization has added the United States to a list of countries where similar types of polioviruses have been found. There are about 30 countries in Europe, Asia and Africa on the list.

The US was officially added to the list last week by the CDC, raising questions about what will happen next. Do people who got all of their vaccine needs need a booster? If you don't know if you've received the vaccine, what should you do?

There isn't a recommendation for fully vaccineed people to get a booster.

There haven't been any national or local recommendations for people who are secure about their childhood vaccinations to need an additional booster. It might be reasonable for someone to seek a booster in certain circumstances.

The person who created the vaccine.

Schaffner told Live Science that the primary concern for health officials is to make sure those who haven't completed their vaccine series are protected.

The director of the CDC's National Center for Immunization and Respiratory says it's important that people in unvaccinated areas get up to date on the vaccine. There is no cure for the disease, and it is a dangerous one.

Baseline polio vaccine recommendations

The CDC says that since 2000 the U.S. has only used the inactivated vaccine, a shot that's typically injected into the arm or leg. The oral vaccine was halted in the U.S. because it contained live, but weakened, polioviruses. The weakened viruses can be shed in the stool of people who have not beenvaccinated and can evolve to cause illness and possibly paralysis in people who have not beenvaccinated.

Because of this risk, the U.S. only administers the IPV, but "vaccine-derived" polioviruses can still be imported from places that use the OPV.

Schaffner said that it shows how vulnerable we are to foreign imports.

The CDC recommends that U.S. children get four doses of the vaccine, one for each of the following ages: 2 months old, 4 months old, between 6 and 18 months old, and between 4 and 6 years old. The CDC has a number of "catch-up schedules" for children who get delayed between vaccinations.

If you have never received a vaccine for the disease, you should get three doses. The CDC recommends that these people get their first dose anytime, get the second dose one to two months later, and get the third dose six to 12 months after that. Adults who have only received a single or two doses in the past should seek additional doses.

Most people in the U.S. don't need to get boosters for their vaccine series until they're older. Schaffner said that this was a testimony to the protection you get from the vaccine.

illustration of poliovirus particles

Poliovirus most commonly spreads through contact with the feces of an infected person. (Image credit: KATERYNA KON/SCIENCE PHOTO LIBRARY via Getty Images)

Since 1955, the shots have been recommended as routine vaccinations, according to Verify. If an adult has gotten at least three doses of either the IPV or the tOPV, they are considered fully vaccine free. According to the CDC, an adult is fully protected if they've received four doses of any combination of the IPV and the tOPV.

Paralytic polio can cause permanent disability and death if it enters the central nervous system and causes weakness in the arms, legs or both. The CDC says that three doses are 99% protective.

Africa has been declared free of the vaccine that causes the disease.

Who needs a polio booster?

There are instances in which fully-vaccinated adults might consider a booster.

If you work in a lab or health care setting where you handle specimen of the disease, you should get a booster. If you're traveling to a country with a higher risk of exposure to the disease, you may want to get a booster. The Global Polio Eradication Initiative states that long-term visitors should get an IPV booster between four weeks and one year prior to travel to Afghanistan and Pakistan. There are no similar recommendations for the US.

An unvaccinated adult in Rockland County was the only person in the U.S. to have been diagnosed with the disease. The New York State Department of Health reported that the disease was found in wastewater samples from Rockland County.

The health department recommends that New Yorkers get a vaccine to fight the disease.

  • Individuals who will or might have close contact with a person known or suspected to be infected with poliovirus or such person's household members or other close contacts.
  • Health care providers who work in areas where poliovirus has been detected and might handle specimens that might contain polioviruses or who treat patients who might have polio. 
  • Individuals with occupational exposure to wastewater.

An expert at the Columbia University Vagelos College of Physicians and Surgeons said in a statement that people who have weakened immune systems may want to consider a booster. If you don't know how many vaccine doses you've received, you might consider getting boosted.

According to the Morbidity and Mortality Weekly Report, there are some tests that can be used to assess vaccine status, but they aren't recommended because there isn't a lot of access to the tests. serologic testing can no longer be used to assess immunity because of the lack of testing for all 3 types.

Schaffner said that the risk of exposure for US residents beyond New York is negligible. Even if you live in New York, you should still get your vaccine because you could be exposed to the disease on a plane.

The vaccine is very good at preventing the most severe potential effects of the disease, but people who received the vaccine could still be carriers of the disease.

According to the Pan American Health Organization, if a person is ever exposed to the pathogen, they can still pass it on to someone else. The IPV doesn't generate as much immunity in the intestines as it would in the blood.

About polio

According to the CDC, it can be transmitted through respiratory droplets that are released when a person sneezes or coughs, but it's less common than most people think. It is possible to prevent the spread of the viruses by washing your hands with soap and water.

The majority of people who catch the disease don't show any symptoms. About 25% of people develop flu-like symptoms. A small percentage of people with infections develop severe symptoms, such as meningitis, an inflammation of the tissue surrounding the spine and brain, which can lead to death.

Post-polio syndrome is when a person who seems to have recovered from the disease develops new muscle pain, weakness or paralysis decades later.

It was originally published on Live Science