Poliomyelitis is an ancient disease that has resulted in significant morbidity and mortality worldwide for centuries. Its history is complicated by changes in the way humans adapt and live, and advancements in prevention and treatment were fueled by human emotion and personal experience that have been rarely rivaled throughout history. The progression of the fight against polio has shown us the life-saving power of vaccines, the unexpected impact of improved hygiene and quality of life on disease transmission and the impact of global collaboration and discovery.
What is Polio?
Poliovirus is a member of the genus Enterovirus within the family Picornaviridae. Poliomyelitis is a highly infectious disease caused by poliovirus that tends to impact children most significantly. The disease is spread from person to person via the fecal-oral route or when someone comes in contact with food or water containing infected fecal material. Once inside the body, the virus replicates in the oropharyngeal and intestinal mucosa. From this point, the virus moves into the cervical and mesenteric lymph nodes (lymph nodes in the membrane that connects the bowel to the abdominal wall), followed by the blood, causing viremia that results in a flu-like illness. This will be the result for most people infected with poliovirus, particularly if they have some existing level of immunity. However, the virus sometimes invades the nervous system and causes paralysis. One in 200 infections lead to irreversible paralysis, and among those paralyzed, up to 10% will die from the immobilization of muscles required for breathing. There is no cure for polio; only immunization can break the infection cycle.
Poliovirus Across History
Polio epidemics were not documented or well-described until late in the 19th century. Sporadic cases have been noted throughout history, most famously in ancient Egyptian art depicting figures with tell-tale signs of paralytic polio, such as withering and deformity of the legs and feet. In 1789, a pediatrician in London published the first clear description of paralytic polio in children. However, cases were only reported sporadically at that time. Because polio requires a human host and does not survive outside the human body for longer than 1-2 weeks, the disease could not spread as readily until people started living in closer, larger groups.
In the late 1800s, epidemics started occurring in industrialized nations across Europe and the U.S. Following small epidemics in Norway and Sweden, the first large outbreak occurred in the U.S. (Vermont) in 1894, resulting in 132 cases of infantile paralysis. From there, the disease erupted further, leaving panic, horror and superstition in its wake. At its peak, the virus caused 21,000 cases of paralytic poliomyelitis and 3,000 deaths in 1952. By the mid-20th century, the disease had spread globally and impacted over half a million people annually. Those who were infected but did not die of the disease were often left to face significant morbidities, including chronic pain and permanent paralysis requiring the use of crutches, wheelchairs, an iron lung or other respiration devices to help them breathe.
The Impact of Improved Hygiene on the Spread and Seriousness of Polio
It makes sense that improved hygiene and sterility help prevent the acquisition of diseases that require fecal-oral transmission, such as polio. However, when hygiene improved in the 19th century across industrialized countries, there was an unexpected effect on the spread of polio amongst infants: cases of severe poliomyelitis actually increased. Scientists believe that polio was quite common throughout history, but that people were exposed more often due to poor living conditions and unhygienic environments. Exposed birth parents offered immunity to their babies during pregnancy and through breastmilk. This was helpful, as babies with maternal immunity were more likely to fight off the disease early, when it mimics a flu-like illness. Babies in clean environments were no longer exposed to the disease at the early ages when they still had some maternal immunity, putting them at risk for contracting the disease later in life when it was more likely to be severe.
The March of Dimes and its Impact on Polio Research
In 1921, former President Franklin D. Roosevelt was infected with poliovirus, which led to permanent paralysis in his legs. At the time, public knowledge of any disability or weakness in a political leader was strongly stigmatized and discouraged, and the physical and mental strength that Roosevelt demonstrated in the face of difficult circumstances had a significant impact on the world.
Roosevelt also dedicated years of his life to advocating for victims of poliovirus infection. In 1926, he helped establish a rehabilitation center in Warm Springs, Ga. to aid other polio victims. Leadership of the center was later transferred to his law partner, Basil O'Connor, who expanded the initiative into a nonprofit foundation and launched the National Foundation for Infantile Paralysis. Fundraising initially relied on charitable events, including annual birthday celebrations for the president, but the demand for funds grew as the number of polio cases continued to rise.
What followed would mark a novel and significant moment in American philanthropy efforts. In 1938, a new fundraising strategy called "The March of Dimes" was introduced. This strategy proposed that every person would be able to support polio victims regardless of their own means or status, even if this meant only contributing a dime. The public was encouraged to send dimes directly to the White House. The campaign, which leveraged popular media and entertainers, was highly successful. This initiative not only helped to fund patient care and polio research, but also demonstrated the power of mass public involvement in charitable causes. Ultimately, this fundraising supported the research that led to the development of the polio vaccine by Jonas Salk in 1955.
The March of Dimes campaign underscored the critical role of collaboration and effective communication in rallying public support for health initiatives, demonstrating that when the public is fully engaged and informed, collective efforts can drive transformative progress in disease prevention and medical advancements.
Vaccines
Early Work Leading to Polio Vaccine Development
Still, with polio becoming one of the most feared diseases in the late 19th and early 20th centuries, the world was desperately looking for a vaccine. The first breakthrough occurred in 1949. A trio at Boston Children's Hospital, John Enders, Thomas Weller and Frederick Robbins, were able to grow the poliovirus in human tissue in a laboratory. This milestone accomplishment resulted in the 1954 Nobel Prize. Isabel Morgan and Dorothy Horstmann were also instrumental in the successful journey to a polio vaccine. Morgan's work helped us understand that there are 3 distinct types of poliovirus (serotypes 1, 2, 3), that killed virus could be used/effective for vaccinations and that booster doses would support longer immunity. Horstmann's group helped elucidate that poliovirus infects the gastrointestinal tract, which ultimately led to the support for an oral polio vaccine.
Inactivated Polio Vaccine
Once the virus could be grown in cell culture, vaccine research and trials began in earnest. In the 1950s, 2 versions of a polio vaccine were found to be effective in preventing poliovirus infection/disease. The first was an inactivated killed-virus vaccine developed by U.S. physician Jonas Salk. In 1953, Salk tested the vaccine on himself and his family. He also tested the vaccine on children who had recovered from polio and found that their antibody levels increased after vaccination. As a result, 1 year after he tested the vaccine on himself and his family, one of the largest field trials in medical history was conducted. Salk's vaccine was tested successfully on over a million children in Canada, Finland and the U.S., and the vaccine shown to be safe, 90% effective against serotypes 2 and 3 poliovirus and 60-70% effective against type 1. With 1961 arriving, cases had fallen to only 161 per year, compared to the 20 thousand documented cases approximately 10 years earlier.
In perhaps one of the most humanitarian acts of our time, Salk realized that the entire world needed this vaccine, and it was needed at low- or no-cost if efforts to eliminate this deadly virus were to be successful. He was committed to equitable access to his vaccine and did not profit from sharing the formulation or production process with the 6 pharmaceutical companies who were licensed to produce inactivated polio vaccine (IPV). Famously, in a 1955 interview, when asked who owned the patent for IPV, he replied, "Well, the people, I would say. There is no patent. Could you patent the sun?"
Oral Polio Vaccine
Later in the 1950s, Albert Sabin, a physician and microbiologist, developed a second polio vaccine. Unlike Salk's IPV, this vaccine was delivered orally (oral polio vaccine, or OPV). His vaccine was also different from Salk's in that it was live-attenuated (using the live virus but in weakened form) and was typically given by liquid drops or on a sugar cube. There was initially little interest in this vaccine, since Salk's IPV was so successful in the U.S., and the concept of a live-attenuated vaccine was relatively new at the time.
The first test of a live-attenuated polio vaccine on humans was conducted in 1950 by Hilary Koprowski on 20 disabled children in Rockland County, New York. The trial was successful, with all children showing a positive antibody response and excreting the attenuated strain.
Sabin, like Salk, successfully tested the OPV on himself and his family, then teamed up with a group of Russian virologists to test the vaccine more broadly. Mikhail P. Chumakov was responsible for testing the Salk vaccine in the Soviet Union. Using an attenuated seed virus provided by Sabin, Chumakov vaccinated over 10 million children from 1958-1959. The OPV proved safe and effective; these findings were independently endorsed by the World Health Organization (WHO) to mitigate public distrust circulating during the Cold War.
While both vaccines were critical and effective for global reduction and eradication of polio in many countries, the OPV did have some important advantages versus the IPV. Sabin's OPV was more easily delivered to children via the oral route, and it helped break the transmission chain between children, unlike Salk's IPV version.
Huge Progress and Ongoing Challenges on the Road to Eradication
In 1985, Rotary International launched a global effort to immunize the world's children against polio. And in 1988, The Global Polio Eradication Initiative (GPEI) was founded, a public-private partnership led by national governments with 6 core partners: WHO, Rotary International, the U.S. Centers for Disease Control and Prevention (CDC), the United Nations Children's Fund (UNICEF), the Bill & Melinda Gates Foundation and Gavi, the Vaccine Alliance. The goal of the GPEI is to eradicate polio worldwide. When the GPEI's was founded, polio was endemic in 125 countries and still paralyzed over 1000 children every day around the world.
Since that time, the collaborative work of over 200 countries and about 20 million volunteers have resulted in over 2.5 billion childhood polio immunizations, leading to a 99.9% global decrease in the incidence of polio. Today, polio remains endemic only in 2 countries-Pakistan and Afghanistan. The global public health community now has 1 primary task: to eliminate polio in these last few strongholds and get rid of the final 0.1% of polio cases to be polio free worldwide.
Although the world continues to make progress on global eradication efforts, there are ongoing challenges to meeting this objective. In June 2024, the war-torn city of Gaza reported that, after 25 years of having no cases, variant poliovirus type 2 (cVDPV2) was detected in environmental wastewater samples. Gaza also reported cases of children having acute flaccid paralysis, including a single confirmed child who tested positive for this polio variant. Laboratory results on the other cases are still pending.
These examples illustrate the fact that conditions in times of crisis (like war) can create environments that are ripe for the spread of pathogens and infectious disease. Fighting, roadblocks and other factors that limit access to clean water, sanitation and basic health care (including medical supplies and vaccines) can allow a virus like polio, which can survive for days to weeks outside its human host, to gain a foothold. The WHO is working with Gaza and other partners to deliver and utilize novel oral polio vaccine (nOPV2) to protect against paralysis and community transmission of cVDPV2 in Gaza.
A Brighter Future
The history of polio, from its ancient origins to its near eradication, illustrates the profound impact of scientific advancement, public health initiatives and global collaboration. The development and widespread administration of polio vaccines highlight the power of public support and innovative fundraising in driving medical breakthroughs. Today, thanks to global efforts, polio is on the brink of eradication, with only a few strongholds remaining, signifying a remarkable achievement in public health and a testament to the effectiveness of coordinated global action.
Why do cases of polio continue to crop up in non-endemic countries across the globe (places like Gaza, where the disease has been eliminated for years)? While oral polio vaccines are key to polio control efforts, they've also contributed to the problem in the form of circulating vaccine-derived polioviruses. A new vaccine might offer a solution and help are pave the road to eradication.
