Vaccine-related cases of polio nearly eradicated

The risk of the polio vaccine causing the disease appears to have been eliminated in the United States because of a switch to a vaccine containing an inactive form of the virus.

“The only threats from polio in the United States are from laboratories and the few remaining polio-endemic areas in Africa and Asia,” the national Centers for Disease Control and Prevention in Atlanta said Tuesday.

Introduced in 1961, the polio vaccine contained the paralyzing illness. But rare cases triggered by the vaccine have only recently been wiped out, according to the report in the Journal of the American Medical Assn.

An average of nine U.S. cases of poliomyelitis a year were blamed on the oral vaccine that contained weakened strains of the virus. But beginning in 1997, a gradual shift to an injectable vaccine that contains inactivated strains of the virus has eliminated vaccine-associated cases since 2000, the report said.

The older vaccine triggered the illness in one in 2.9 million cases, the study said.