“My daughter went in for her kindergarten physical and they gave her the polio shot. Why didn’t they give her the vaccine you swallow?”

The story behind this question is one of the success stories in infectious diseases. A disease that paralyzed and killed so many children and adults from just 50 years ago is on the verge of being eliminated.

Polio was first described in 1840 by a German orthopedist named Jacob von Heine. Much later, it was found to be caused by three viruses in the enterovirus family. The disease, which usually occurred during the summer, would begin with fever, fatigue, headache, vomiting, constipation, stiff neck, and malaise, and progress to gradually paralyze most of those who had it. The paralysis could be temporary but was most often permanent. Initially, people would die as their respiratory muscles would become paralyzed and they would struggle to breathe. One of the major advances in the treatment of polio was the iron lung, introduced in 1928, that would breathe for the patient by increasing and decreasing the atmospheric pressures around the lungs. Still many died from pneumonia and malnutrition. More recently, the respirator and better supportive care have markedly reduced the mortality of this horrendous disease.

Many senior citizens may remember the “polio scares” of the 1940s and 50s when parents wouldn’t allow their children to play in large groups or even go to the pool in summer. They had an understandable fear of this contagious and potentially devastating disease.

In 1949, John Franklin Enders developed a way to grow the polio viruses and Jonas Salk went on to develop a “killed vaccine” in 1954. A killed vaccine contains no live virus and does not cause illness. There are potential side effects due to the injection of this vaccine or the body’s reaction to it.

In 1960, Albert Sabin developed a “live vaccine” which could be administered orally. Most of us received that vaccine on a sugar cube but more recently babies have received this vaccine by simply drinking a liquid preparation. This vaccine is produced by changing the active (or wild) viruses to make them incapable of causing paralysis but still capable of causing the immune system to develop antibodies to the three polio viruses.

The Sabin vaccine had the advantage of not requiring an injection but had the disadvantage that, in a very tiny number of people, the viruses could change inside the person to the active virus and cause polio in the individual receiving the vaccine or those who were around them. This extremely rare complication occurred in between two and 10 people every year in the United States.

The success of the vaccines was phenomenal. In the United States, polio cases were reduced from over 50,000 per year to virtually none in 1980 (except those two to 10 cases actually caused by the Sabin vaccine and a few imported from other countries). Worldwide, the number of cases went from 35,000 reported in 1988 to 3,500 last year. With increased vaccine coverage, the World Health Organization predicts that there will be no new cases of wild polio this year. To account for small pockets of unreported polio, immunization will be continued through 2005 to 2010, but no further immunization will be needed thereafter!

Although the oral Sabin vaccine has accounted for much of the decrease in polio cases, it has outlived its usefulness. In order to eradicate the illness totally, those two to 10 cases must also be eliminated, so for now, we will be using exclusively the Salk polio shot. By no longer giving the oral vaccine, we can prevent those vaccine-caused cases of polio from occurring. We can make the polio viruses extinct in the next decade.