A Model Definition/Categorical Argument
How many children will we need to paralyze to eradicate polio forever? Increasingly, as we approach the ultimate goal of eliminating a crippling disease once and for all from the planet, we must confront this grim calculation. Until the turn of this new century, the naturally-occurring—or wild—polio virus was the primary way for the disease to reach its human hosts, causing illness, debilitation, partial or total paralysis, even death, usually of children, almost always in remote villages ill-served by health agencies. But since the certified eradication of Type 2 polio, and the near elimination of Types 1 and 3, the primary way polio infects its hosts is, I hesitate to say it, through our own inoculation campaigns.
The twentieth-century eradication of smallpox must have emboldened us to imagine that ridding the world of polio would be a matter of course. After all, according to Donald Henderson’s “The Eradication of Smallpox—An Overview,” smallpox had killed 300 million people in the 20th century alone, “more than twice the death toll of all the military wars of that century.” Compared to that massive, almost always deadly scourge, polio, which paralyzed children but killed few and was almost never contracted by adults, must have seemed like an easy target for elimination.
But polio turned out to be a different case altogether: less deadly but sneakier, more resistant to both serums and human effort.
First of all, smallpox is easy to spot. As Henderson again notes, this time in “Countering the Posteradication Threat of Smallpox and Polio,” smallpox is readily visible. Sufferers are covered over most of their body with distinctive purulent poxes. Unlike polio, which can hide in the body for years while its bearers infect others, smallpox advertises its presence and makes intervention much more likely. Imagine trying to rid the world of a disease that has more than 200 asymptomatic carriers for every paralyzed patient.
Second, polio vaccines need to be administered several times, on a schedule, to be effective. Whereas for smallpox, again according to Henderson, a single dose of vaccine immunizes nearly 100% effectively, polio requires at least three doses of Oral Polio Vaccine (OPV). And fewer than six doses might not achieve a 90% protection against the predominant strains: types I and III. In stable communities with the enthusiastic support of the local population and health agencies, inoculating every child under five with six doses of anything on a scheduled basis would be seemingly indomitable. But, add to that the social and environmental instability of the areas where polio is endemic (Afghanistan, Pakistan, North and West India, and Nigeria), where flood, famine, and warfare shred the social fabric, and the job seems beyond human capability.
Finally, the vaccines themselves can infect patients with the virus. This is the most insidious and infuriating frustration of the fight against polio. What at the start of the campaign was an almost negligible nuisance factor (if lifelong paralysis can be discounted) of 1 case per 3 million doses of vaccine, has become—tragically and ironically—a much more significant drawback of the seemingly endless effort to finally eradicate polio.
Aylward and Tangermann relate the confident enthusiasm of the polio eradication campaign of the early 1980s, fueled by a strong start and rapid success.
By the year 2000, the incidence of polio globally had decreased by 99%. . . . By 2002 . . . the Americas, Western Pacific and European Regions had been certified polio-free. By 2005, . . . wild poliovirus (WPV) had been interrupted in all but 4 ‘endemic’ countries: India, Nigeria, Pakistan and Afghanistan, where eradication efforts effectively stalled.
Momentum is everything in eradication campaigns. The effort is global and requires the cooperation of entire continents. Adversaries in everything else need to put aside their differences—sometimes even calling cease-fires on battlefields—to cooperate in delivering preventive measures to diverse populations regardless of their race or nationality. What had occurred so naturally in the eradication smallpox needed to occur again if polio was to be eliminated. Henderson described it this way:
The scope of the smallpox program was unprecedented. It required the cooperation of all countries throughout the world and the active participation of more than 50. It was a universal effort unlike any that had ever been undertaken. Most countries eventually proved to be readily responsive but strong persuasion was necessary for some. National antipathies were generally set aside.
In both efforts, the vast majority of the population in endemic countries were inoculated in the early years. And in both cases complications of population movement, natural disasters, maddening bureaucracy, and dislocations of regional conflicts and civil wars frustrated the mass inoculations. But the polio campaign has not yet overcome the elemental differences of the two diseases that make the ultimate elimination of polio so much less likely.
Like the smallpox campaign, the effort to eradicate polio scored impressive early successes. According to Aylward and Tangermann, “By the year 2000, the incidence of polio globally had decreased by 99% compared with the estimated number of cases in 1988 . . . and the last case of polio due to wild poliovirus type 2 transmission anywhere in the world was recorded in Uttar Pradesh, India in 1999.” And then the effort stalled.
Polio is not smallpox: obvious, defenseless, stable. It’s nefarious, invisible until it strikes, and mutable. The 1% of cases that persisted after 2005 began to mutate. The world had failed to wipe out the last of the last viruses. Some children had only mucosal immunity while the virus thrived in their intestines. The carriers looked healthy but passed the virus to others undetected, especially in the toughest places, the remote villages and refugee camps where sanitation was crude at best and healthcare nonexistent.
And while the agencies assigned to eradication tried to counter the mutations with customized variations of the Oral Polio Vaccine to meet local conditions, mounting resistance to an intrusive, expensive, and seemingly endless global eradication effort weakened the support needed to force the effort past the last 1%. According to Taylor, Cutts, and Taylor, in the American Journal of Public Health, “Negative effects were greatest in poor countries with many other diseases of public health importance.” It’s not hard to imagine the reluctance of villagers in India, for example, whose children routinely die of diarrhea, objecting to the massive effort to eliminate polio, which many have never seen, and which does not kill.
There was blessed, magnificent, altogether positive enthusiasm at the UN, at the WHO, at Rotary International, in the 1980s, that the world could once again achieve with polio the triumph of man over disease that had been accomplished against smallpox. But similar efforts achieve similar results only when conditions are similar, and smallpox and polio are too different for the same formulas to work.
Aylward, B., & Tangermann, R. (2012, April 06). The global polio eradication initiative: Lessons learned and prospects for success. Retrieved February 12, 2018, from https://www.sciencedirect.com/science/article/pii/S0264410X11015994?via%3Dihub
C E Taylor, F Cutts, and M E Taylor. Department of International Health, Johns Hopkins School of Hygiene and Public Health, Baltimore, MD 21205, USA. “Ethical dilemmas in current planning for polio eradication.”, American Journal of Public Health 87, no. 6 (June 1, 1997): pp. 922-925.
Henderson, D. A. (2002, January 01). Countering the Posteradication Threat of Smallpox and Polio | Clinical Infectious Diseases | Oxford Academic. Retrieved February 12, 2018, from https://academic.oup.com/cid/article/34/1/79/312029