Oral Polio Vaccine
The oral polio vaccine is quite effective in preventing the disease. However, because it poses a slight risk of a rare but serious condition, its use in the United States has been discontinued -- an enhanced-potency inactivated polio vaccine is now used instead. The oral vaccine is still used for polio prevention in many other parts of the world.
Oral polio vaccine (OPV) contains live but weakened poliovirus. It is highly effective in polio prevention. However, because of the risk of a rare but serious condition called vaccine-associated paralytic poliomyelitis, use of the oral polio vaccine in the United States was discontinued in 2000.
A 1916 polio epidemic in the United States killed 6,000 people and paralyzed 27,000 more. In the early 1950s, there were more than 20,000 cases of polio each year.
The first polio vaccine was licensed in 1955. This was an inactivated polio vaccine (IPV), meaning it did not contain any live poliovirus. By 1960, the number of cases had dropped to about 3,000. In 1961, an oral vaccine was licensed. Following its introduction, as the number of cases continued to drop. In 1979, the last cases of paralytic poliomyelitis caused by wild poliovirus in the United States occurred.
The success of polio vaccination in the United States and other countries sparked a worldwide effort to eliminate this disease.
In 1998, an enhanced-potency inactivated polio vaccine became available. Because oral polio vaccine can cause a rare but serious reaction called vaccine-associated paralytic poliomyelitis, its use was not recommended. In 2000, the use of this vaccine in the Unites States was discontinued.
Oral polio vaccine is highly effective in producing immunity to poliovirus. A single dose produces immunity in approximately 50 percent of recipients. Three doses will produce immunity to all three poliovirus types in more than 95 percent of recipients. As with other live-virus vaccines, immunity from oral polio vaccine is probably lifelong.