Risk of vaccine-associated paralytic poliomyelitis in Latin America, 1989-91.

A major factor influencing the success of poliomyelitis eradication in the Americas was the reliance on mass immunization campaigns with oral poliovirus vaccine (OPV). As global poliomyelitis eradication activities accelerate and campaign vaccine delivery strategies are applied elsewhere, it is critical to determine whether the risk of vaccine-associated paralytic poliomyelitis (VAPP) is altered when routine delivery strategies are supplemented with mass immunization campaigns. We analysed all 6043 cases of acute flaccid paralysis (AFP) reported in Latin America over the period 1989-91 in order to estimate the risk of VAPP. The overall risk was estimated to be one case per 1.5-2.2 million doses of OPV administered, compared with one case per 1.4 million doses administered in England and Wales (1985-91) and with one case per 2.5 million net doses distributed in the USA (1980-89). These data suggest that to eradicate poliomyelitis globally, strategies that rely on mass immunization campaigns to supplement routine delivery services, as recommended by WHO, do not appear to alter significantly the risk of VAPP.