In 1997, the Immunization Practices Advisory Committee (ACIP) recommended adoption of a sequential series of two doses of IPV followed by two doses of oral poliovirus (OPV) for all infants and children to decrease the rare occurrences of Vaccine Associated Paralytic Polio (VAPP) that were noted following the administration of live oral poliovirus vaccine.

Vaccine-associated paralytic poliomyelitis (VAPP) has been the only indigenous form of the disease in the United States since 1979. Additional (unreported) cases of VAPP probably occur. The severity of these cases is similar to that of cases caused by wild virus.

Although the risk for VAPP is low (approximately one case to 2.4 million doses distributed, or one case to 750,000 children receiving their first dose of OPV), the Centers for Disease Control and Prevention (CDC) estimated that 30-40 cases of vaccine-associated paralysis would have occurred in the United States during 1997-2000 if the previously recommended poliovirus vaccination practices had not changed.