“The goal of the Global Polio Eradication Initiative is to ensure that no child anywhere will ever again be paralyzed by any form of poliovirus.”
Global Polio Eradication Initiative, a public-private partnership
“It always seems impossible until it’s done.”
Nelson Mandela
I grew up in the pre-poliovirus vaccine era, a time when polio (aka “poliomyelitis” or “infantile paralysis”) was one of the most feared viral diseases in the U.S., killing thousands of American children each summer and paralyzing many more. But Dr. Jonas Salk’s development of the first inactivated polio vaccine (IPV) in 1955 and Dr. Albert Sabin’s subsequent development of an oral polio vaccine (OPV) in the 1960s changed everything. Due to a massive vaccination program, by 1979 wild polio virus had been eliminated in the U.S.
Leaders of the Global Polio Eradication Initiative (GPEI) are pushing hard to eradicate this cruel pathogen from the face of the Earth. While we are on the verge of eradication, we aren’t quite there…yet. The goal of this Germ Gems post is to provide an update on the challenges that need to be surmounted before we can finally say goodbye to the PV for good.
What is poliomyelitis? PV is an RNA virus that is transmitted from person to person by the fecal-oral route. Humans are the only animal at risk of acquiring polio. In most people with a normal immune system, PV infection is asymptomatic. In some people, however, gastrointestinal tract symptoms occur, and in a small minority (about 1%), the virus invades the central nervous system causing paralysis.
Three PV serotypes are recognized: type 1 (PV1), type 2 (PV2), and type 3 (PV3). Each of these three PV types is referred to as a “wild type virus,” designated WPV1, WPV2, and WPV3. Due to intensive vaccination campaigns, WPV2 and WPV3 were eradicated in 2015 and 2019, respectively, leaving WPV1. The only two countries burdened with endemic (ongoing) WPV1 infections now are Pakistan and Afghanistan. (Data current as of October, 2023).
While there is no treatment for polio, both the IPV and OPV vaccines remain highly effective in preventing this highly contagious viral disease. (In Pakistan, authorities are turning to a controversial new tactic to wipe out polio—imprisonment of parents for up to one month if they fail to get their children immunized against polio.) The OPV is easier to administer and has been shown to induce better immunity in the intestinal tract than IPV but it also has the potential to generate viral variants that cause polio. As a result, OPV and has not been used in the U.S. since 2000. It is still used, however, in other parts of the world.
Because the OPV contains live PVs, the potential for development of circulating vaccine-derived PV strains exists. Indeed, a battle is now being waged against just such a PV variant, called circulating vaccine-derived PV2 (cVDPV2). The battle against this culprit is centered in four countries: Democratic Republic of the Congo, Ethiopia, Nigeria, and South Sudan. On July 30, 2024, the WHO announced its prequalification of a novel oral polio vaccine (nOPV2) that targets cVDPV2.
Eradication of PVs. Eradication of a disease means “permanent reduction to zero cases worldwide.” Of the estimated 1,400 human pathogens, only one—variola (smallpox) virus—has been eradicated in 1980 by a heroic vaccine campaign lasting almost two centuries. The GPEI is leading the global effort to eradicate polio by vaccination.
Launched by the World Health Organization (WHO) in 1988, the GPEI is a public-private partnership led by national governments with five partners—the WHO, Rotary International, the Centers for Disease Control and Prevention, UNICEF, and the Bill and Melinda Gates Foundation. As a result of the GPEI’s massive vaccination program, the global incidence of polio plummeted by 99.9% since 1988; an estimated 16 million people are walking today who would have been paralyzed by polio, and more than 1.5 million people are alive who otherwise would have died of the disease.
The present task of GPEI is to tackle polio in its last strongholds and get rid of the final 0.1% of polio cases. As stated by WHO on its website: “Failure to eradicate polio from these last remaining strongholds could result in a global resurgence of the disease.”
Polio threatening to erupt in Gaza. The threat of polio erupting in Gaza is an example of the important role the so-called Social Determinants of Health play in the genesis of many, if not most, infectious disease outbreaks. In my earlier Germ Gems post, “Infectious Diseases That Track With War,” January 26, 2023, I mentioned the new public health discipline of “war epidemiology” or “conflict epidemiology.” It appears that PV may soon be added to the list of pathogens under study in this discipline.
Before the present hostilities erupted in Israel, Gaza had been free of polio for 25 years. Then, on July 19, 2024, cVDPV2 was found in a sewage sample from the Gaza Strip. Given the extraordinary state of collapse of hospitals and the health care system, in general, it is hard to imagine what an outbreak of polio would do in this area of the world.
One week after polio was found in the Gaza sewage sample, the WHO announced that it was sending more the than 1.6 million doses of the nOPV2 vaccine to Gaza. Then in early August, the WHO and UNICEF called for a humanitarian pause in the conflict to allow two rounds of polio vaccination targeting 640,000 children younger than 10 to take place at the end of August and in September. As the WHO has consistently maintained: “As long as a single child remains infected, children in all countries are at risk of contracting polio.”
The GPEI’s goal of eradicating PV should be attainable. But given the military conflicts besetting our globe coupled with vaccine skepticism that exists in certain areas of the world, it is impossible to even hazard a guess as to when that will occur. Nonetheless, when PV is finally eradicated from the face of the Earth, it should be cause for absolutely unbridled exuberance.
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