Recently completed molecular studies of poliovirus isolates suggest that viral replication of vaccine-related polioviruses may have persisted for as long as 7 years in a patient with vaccine-associated paralytic poliomyelitis (VAPP) in whom common variable immunodeficiency syndrome (CVID) previously had been diagnosed. This report summarizes the clinical and virologic data and discusses the possible implications of these new findings for the global polio eradication initiative, which include how and when to discontinue vaccination when polio has been eradicated.