Why did CDC and ACIP change the polio vaccination schedule to an all-IPV series?
The CDC and ACIP changed the polio schedule in 2000 because the only indigenously-acquired polio in the U.S. since 1980 had been due to the oral polio vaccine, while there had been no polio cases due to the wild poliovirus. The ACIP determined that the risk-benefit ratio associated with the exclusive use of the OPV for routine immunization had changed because of the rapid progress in global polio eradication efforts. In particular, the benefits of OPV had diminished in importance due to the elimination of wild virus associated poliomyelitis in the Western Hemisphere since 1991 and the reduced threat of poliovirus importation into the U.S. Conversely, the risk of vaccine-associated poliomyelitis due to OPV, which caused an average of 8-9 reported cases of paralytic polio each year, was judged less acceptable due to the absence of indigenous disease and reduced risk of imported infection. Consequently, in 1996 the ACIP and CDC recommended a transition policy to increase use of IPV and de