Paralytic poliomyelitis in vaccinated children

Paralytic poliomyelitis were observed in two healthy children who both had previously received four doses of standard inactivated poliovaccine (IPV). These children, whose immune defenses were normal, failed to respond to IPV. This absence of antibody response might be related to an insufficient antigenicity of inactivated vaccines, justifying the extensive use of the more potent IPV, now produced on continuous cell lines.