I will never forget March 16, 1975. It had been almost four months since I began working in India’s largest state, Uttar Pradesh (UP), to try to eradicate smallpox.

On that morning, I was contacted about a new case of smallpox. I reached the patient about 1½ hours after she died from an unusual complication, late hemorrhagic smallpox. Her name was Shanti, a 7-month-old child, the daughter of Pyari Lal. She was probably infected by her sibling. Her death was totally preventable, but fortunately she turned out to be the last case of smallpox in UP.

We finally broke the human chains of transmission of that terrible virus. That experience in India taught me how serious vaccine-preventable diseases could be and how powerful vaccines are in preventing these types of tragedies.

The eradication of smallpox showed that effective vaccines can lead to the ultimate goal: the permanent end of a serious affliction of humankind. Smallpox eradication is our generation’s gift to all future generations.

Polio is the next vaccine-preventable disease targeted for eradication. This terrible disease causes severe, lifelong, crippling illness.

As a child, growing up in the United States during the 1950s before polio vaccines were available, I remember the fear and panic that spread through the community at the height of the summer-fall epidemics.

With effective polio vaccines, we eliminated the disease in all of North and South America. Europe and major sections of East Asia have also been certified as polio-free. Now, we have the opportunity to finish the job.

Many of the lessons learned from smallpox eradication have been applied to today’s polio efforts. Using a strategy tailored to the specific vaccine coupled with finding and investigating each individual case are critical for success. They also help to measure progress, inform adjustment of tactics, and identify the need for continued research to develop new tools to achieve eradication.

The world is very close to being polio-free—there has been a 99-percent reduction in cases, compared to when the eradication effort started. We have reduced the number of countries in which polio is endemic from 125 to 4.

But when eradication is the goal, one case is one case too many. It is critical that we continue our work together so that as with smallpox, we make polio history and ensure that no child’s future is crippled by this terrible disease.