In 1994, the United States was declared polio-free.
Scientists say that, today, the polio virus is on the brink of extinction worldwide.
Over the next two weeks, health workers in 155 countries will be doing something that's never been attempted before to hopefully get rid of polio once and for all.
It's a globally synchronized switch, phasing out the current oral polio vaccine in favor of a new one.
- "The world is in the process of trying something it has never attempted before. Over the next two weeks, 155 countries must stop using a vaccine that has been protecting children from paralyzing polioviruses for more than a half-century. Designed in the 1950s, the vaccine has helped take the world to the edge of polio eradication. In the 1980s, polioviruses crippled 350,000 children annually; this year they have maimed 10 in the only two countries where polioviruses still spread, Pakistan and Afghanistan. It has been a monumental achievement in public health. But for a while now, a component of the vaccine has caused more problems than it has solved, and has actually resulted in a relatively small number of cases of paralysis. So between this past Sunday and May 1, all countries that use the oral polio vaccine developed more than 60 years ago must stop administering the current formula and replace it with a new version."
This segment aired on April 18, 2016.