What you need to know
- Before polio vaccines, outbreaks of the disease killed or paralyzed half a million people a year.
- Just one decade after the U.S. approved the first polio vaccine, polio cases were reduced by more than 99 percent.
- A global effort to make polio vaccination universal has eliminated wild polio in all but two countries.
In the late 1800s, the first polio outbreak struck the United States. For decades, polio epidemics plagued communities around the globe, killing or paralyzing hundreds of thousands annually.
Then, in 1955, the first polio vaccine was administered. Just 70 years later, a disease that once terrorized the world has been nearly eradicated.
Here’s a look at how polio vaccines changed the world.
Two vaccines provide nearly 100 percent protection against polio.
Inactivated polio vaccine
The inactivated polio vaccine contains poliovirus that has been killed. IPV is very effective at triggering immunity to polio, providing over 99 percent protection against paralysis in three to four injectable doses.
People vaccinated with IPV have almost no risk of polio. However, if exposed, they can still carry the virus and potentially spread it to others. For this reason, IPV is primarily used in regions where polio is rare.
IPV is an extremely safe vaccine, with no serious side effects linked to it. Since the vaccine doesn’t contain a live poliovirus, it can’t cause polio.
Oral polio vaccine
Oral polio vaccines are liquid drops given by mouth. Unlike IPV, OPV prevents poliovirus from spreading from one person to another. That makes IPV a better choice for regions with higher levels of polio spread.
OPV contains a weakened poliovirus and is 98 percent effective against paralysis from three or more doses. The vaccine is very safe and has been administered to billions of infants and children worldwide.
There is a very small risk (about one in 10 million doses) that the weakened live virus in OPV can leave the body and infect an unvaccinated person, particularly in areas with poor sanitation and low polio vaccination rates. Vaccinated people are well protected against all polioviruses. New OPVs, first introduced in 2021, have a significantly lower risk of causing vaccine-derived poliovirus in unvaccinated people (about one in 100 million doses).
Polio vaccines wiped out polio in the U.S. in under 25 years.
In 1894, the U.S. experienced its first polio outbreak in Vermont, which left 18 dead and 132 paralyzed. Polio spread across the U.S. and Europe in the following decades, including the devastating New York City outbreak of 1916 that killed over 2,000 people.
As polio outbreaks spread, researchers around the world raced to find a way to prevent the deadly disease. The year 1952 marked the peak of polio epidemics in the U.S., with nearly 58,000 cases of paralysis and 3,145 deaths reported.
The following year, the first doses of the polio vaccine were administered as part of a clinical trial involving an estimated 1.6 million children in the U.S., Canada, and Finland.
The vaccine was declared safe and effective in 1955, and millions of children were vaccinated in the following months. Within a decade of the vaccine’s approval, annual polio paralysis cases declined from almost 29,000 to 61. The U.S. has not had a single endemic (not from international travel) polio case since 1979 and was officially declared polio-free in 1981.
Polio vaccines are one of the greatest success stories in medical history.
Reports of polio-like diseases date back thousands of years, including descriptions from ancient Egypt and Rome. The disease circulated at low levels until the 1900s, when global epidemics exploded, eventually paralyzing or killing half a million people each year.
Vaccines dramatically reduced polio in many countries—but much of the world did not have access and still suffered from regular outbreaks. In 1988, the Global Polio Eradication Initiative launched to ensure that children in every part of the world are vaccinated against polio.
Timeline showing important milestones in the history of polio eradication.
Since GPEI’s launch, more than 3 billion children have received polio vaccines, including children in extremely remote regions and conflict zones. Polio vaccines have prevented 20 million polio paralysis cases and 1.5 million childhood deaths since 1988, according to GPEI.
In 1994, one century after the first known polio case in the U.S., the Americas were certified polio-free. Between 1994 and 2020, five of the six world regions were declared polio-free, accounting for 90 percent of the world’s population.
Global polio eradication efforts have eliminated polio in all but two nations.
For the first half of the 20th century, polio was endemic in every country, meaning the disease was circulating continuously around the world. Today, polio is endemic in only two countries: Pakistan and Afghanistan.
This progress was made possible by global efforts to improve living conditions and make polio vaccines universally available.
Individual hygiene and community sanitation initiatives have been essential in reducing polio. Access to clean water, basic sanitation, and hygiene practices like handwashing help prevent polio spread. However, vaccines are the single most important tool in the fight against polio.
Vaccine opponents have falsely claimed for decades that improved sanitation is the main reason for polio’s decline. While it is one contributing factor, we know that claim isn’t true because areas that lack reliable access to clean water and sanitation have still been able to eliminate polio by maintaining high vaccination rates.
Additionally, at its height in the 1950s, polio affected countries like the U.S. that had widespread access to clean water and indoor plumbing. Polio outbreaks can still strike developed countries when immunization is low.
If you have questions about the polio vaccine, talk to your health care provider.