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Seventy years after the release of the polio vaccine developed by Jonas Salk, MD, polio vaccination remains critical.

Since the vaccine’s development, the number of infections, paralyses, and deaths caused by poliovirus has dropped significantly worldwide. Polio has largely disappeared in many countries, including the United States. However, it remains active in a few small pockets of the world and still has the potential to spread, including in the U.S.

Communities with low vaccination rates are most at risk for polio’s spread. Vaccination is critical to prevent a widespread comeback of polio.

“If we don’t have the commitment (of) the whole community, this virus, like other viruses, could certainly return, and we could start seeing cases where people are infected again and children are paralyzed again,” says Andrew Nowalk, MD, clinical director, Division of Pediatric Infectious Diseases, UPMC Children’s Hospital of Pittsburgh.

What Is the Polio Vaccine?

The polio vaccine protects against poliovirus, an infectious disease that can affect the nervous system. There are three types of poliovirus. It typically spreads through contact with a contaminated person’s feces — either directly or by touching a contaminated surface — and then touching your mouth.

Poliovirus infection can cause flu-like symptoms; in severe cases, it can cause paralysis and death. In 1952, polio caused more than 20,000 cases of paralysis and 3,000 deaths in the United States.

The development of the polio vaccine caused a sharp decline worldwide in polio cases, as well as paralysis and death. Dr. Salk’s vaccine, which he developed at the University of Pittsburgh, became the first licensed polio vaccine in 1955.

The polio vaccine is effective at preventing infection. It’s especially effective at preventing severe disease, paralysis, and death.

There are two major polio vaccines:

• The inactivated polio vaccine (IPV) — This contains an inactive form of poliovirus that you get by injection. It’s also known as the Salk vaccine in honor of Dr. Salk. The inactivated vaccine is the only polio vaccine used in the United States.
• The oral polio vaccine (OPV) — This vaccine contains a weakened (or “attenuated”) form of poliovirus that you get via drops on the tongue. It’s also known as the Sabin vaccine in honor of Albert Sabin, MD, who developed it. The oral vaccine is no longer in use in the United States but is in use in many areas worldwide.

Although it’s still possible to get and spread poliovirus after getting vaccinated, the vaccine protects against severe disease.

“The vaccine is amazing. It’s incredibly protective,” Dr. Nowalk says. “So, despite the fact that it doesn’t give you protection against spread … we loved it because it really prevented disease.”

Is Polio Vaccination Still Necessary?

Polio cases have plummeted since the development of the vaccine. However, polio vaccination still remains critical because the disease isn’t eradicated.

Type 1 polio is still active in some areas of the world. Also, a new type of polio developed from the oral polio vaccine. Known as vaccine-derived poliovirus, it can spread when the weakened virus from the OPV enters a community with low vaccination rates.

Polio can spread worldwide through travel. For example, if someone infected with polio enters the United States and encounters a community with low vaccination rates, polio may spread.

In 2022, an unvaccinated young adult from New York developed a case of vaccine-derived poliovirus that partially paralyzed them. The virus likely came into the community from someone traveling.

“The reason we are so focused on keeping vaccine rates high is precisely because of the world’s ability to allow people to travel at will very rapidly,” Dr. Nowalk says.

“What we need to do is to not have susceptible communities. We need to have our communities really promote vaccination rather than let vaccination rates fall. Because if we make sure our vaccination fence is up, that’s really going to prevent polio from coming in.”

Dr. Nowalk says widespread community polio vaccination also protects children who can’t get the vaccine. Children with compromised immune systems — either from medical treatments or medical disorders — can’t get vaccinated.

“Those folks often can’t choose to be vaccinated because they’re on a medicine or their body’s makeup is such that they don’t have the immune system to protect them,” Dr. Nowalk says. “They’re depending on us as their community to protect them.”

Community vaccination can prevent the spread of polio and especially severe outcomes like paralysis and death.

“I look at vaccines as seat belts,” Dr. Nowalk says. “We have laws for seat belts to make sure we put our kids in seat belts. And we spent a lot of time when you put a baby in the car, making sure they’re in the right car seat — and children as well. It’s just good common sense because we can keep them safe from injury.

“That’s what vaccines are. They’re the seatbelts of infectious disease.”

Who Can Get the Polio Vaccine?

The Centers for Disease Control and Prevention (CDC) recommends children receive the Salk vaccine as follows:

• First dose — At 2 months old.
• Second dose — At 4 months old.
• Third dose — Between 6 and 18 months old.
• Fourth dose — Between 4 and 6 years old.

Four doses provide full protection.

A 2023 CDC report stated that 93% of United States kindergarteners had gotten vaccinated against polio.

However, older children and adults who were not fully vaccinated against polio when they were younger can still get vaccinated. Talk to your primary care provider or your child’s pediatrician about how to get yourself or your child vaccinated.

“They’re going to get you the right vaccine that’s needed, and you’re going to get protected,” Dr. Nowalk says.

Is the Polio Vaccine Safe?

The polio vaccine is safe and effective. After safety incidents in the vaccine’s early days, the United States strengthened vaccine safety protocols. Today, vigorous reporting protocols help maintain vaccine safety.

The internet and social media can cause misinformation about vaccines to spread easily. But the polio vaccine has proved safe for decades, Dr. Nowalk says.

“I try to emphasize to parents that these vaccines are safe,” Dr. Nowalk says. “We have much bigger safety networks now than we ever had before for vaccines.”

Dr. Nowalk encourages people with questions about the polio vaccine to talk to their doctor or their child’s pediatrician.

“The best place to learn about (polio) is sitting across from your pediatrician or your family medicine provider for your child or your primary care physician for you as an adult,” he says.

“Be confident that your provider is going to give you the right information. Because it all comes down to the one thing I know for sure: I want your child to be healthy the same way you do. We’re all on the same page.”