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Conquering Polio

Fifty years ago, a scientific panel declared Jonas Salk's polio vaccine a smashing success. A new book takes readers behind the headlines


 

The Long Goodbye
Although vaccines have eliminated polio in most of the world, the crippling disease lingers in a few outposts

One of the great ironies of polio in the developed world was that it was a disease of good sanitation. Scattered cases of infantile paralysis had occurred for millennia, but they first began to blossom into epidemics in the 19th century—the era when indoor bathrooms and sealed plumbing were keeping hands cleaner and sewage more contained than ever before. Yet not only did polio outbreaks become more common, they became particularly so in places like Sweden and New York City, where homes were especially well piped and people especially well scrubbed.

The explanation was that while poliovirus in human waste could spread the disease, it could also inoculate against it, exposing infants and young children to frequent mild infections that caused few if any symptoms but provided a long-term load of antibodies. Remove that low background exposure and people were helpless against a strong strain of the bug that might hit you later. That made a vaccine necessary.

In 1956, the year after the Salk vaccine was approved and began being used, the polio case total in the United States was cut nearly in half, to 15,140. In 1957, it was cut by another two-thirds, to just 5,485. The number stabilized in 1958 and actually rallied a bit to 8,425 in 1959—mostly due to the failure of some families to ensure that their children completed the entire three-shot cycle the vaccination required. That scared a lot of complacent parents, who swarmed back to doctors’ offices and vaccination centers. In 1961, only 1,312 American children contracted infantile paralysis, a 98 percent improvement over the epidemic of just nine years earlier. The poliovirus, it was clear, had been nearly eliminated from the U.S. population.

In 1961, Albert Sabin of the University of Cincinnati perfected a vaccine made from a live, weakened virus that was thought to provide a more lasting immunity and had the additional advantage of being administered by sugar cube or dropper. The Sabin vaccine became the preferred method for immunization and eventually knocked the national case count down into single digits.

It turned out that a few cases were brought on by the Sabin vaccine itself, as some of the weakened viruses mutated back to a dangerous state. With that risk considered unacceptable—and with the additional danger that vaccinated children could pass the live virus to family members with weakened immune systems, for whom even a hobbled virus could be deadly—the Centers for Disease Control directed in 2000 that the Salk vaccine once again be used as the principal means of controlling polio in the United States. Today, the Salk vaccine is again a standard part of the childhood vaccine regimen.

Officials say that the last wild case of polio in the United States appeared in 1979. South America declared that polio was eradicated there in 1994. Europe eradicated the disease in 2002. The world’s remaining wild cases, numbering just over 1,200 in 2004, occur in six countries: Afghanistan, Egypt, India, Pakistan, Niger and Nigeria. The World Health Organization (WHO) along with Rotary International and other private charities have set 2005—fifty years after the first mass vaccination began—as the year to eliminate polio globally. WHO organizers rely on the Sabin vaccine for their inoculation project, since it is easier to administer. Even if it does cause some vaccine-associated polio cases, that risk is thought to be offset by the vastly greater number of people who will be protected by it.

While the program has gone well, there is growing doubt that the eradication goal can be reached this year. Rumors that the vaccine caused sterility in children led some communities to refuse the vaccine. By the time the lie was exposed, small polio brush fires had popped up in several countries. Undoing that damage could push the final victory over the disease to 2006 or beyond. Nonetheless, the WHO still insists that polio is headed for extinction—and soon.

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