Strategies for elimination of poliomyelitis in different parts of the world with use of oral poliovirus vaccine.

Since its first mass use in 1960, oral polio vaccine ( OPV ) has largely eliminated paralytic poliomyelitis from temperate-climate and subtropical regions of the world that have good health services and a combined total population of almost 2,000 million people. The various strategies used in these countries have been highly successful even where, as in the USA, large numbers of children received no vaccine or only a single dose of OPV . During the period of 1981-1982, only 2.8 cases per 100 million total population per year were reported in the USA. The main challenge in the present era is the economically undeveloped tropical and subtropical regions with inadequate health services that are inhabited by more than half of the world population, where recent surveys for residual paralysis due to poliomyelitis have shown that the incidence of the disease has been higher than it was in the USA and other predominantly temperate-climate countries before the vaccine era. The problem in these countries is that the majority of children receive no vaccine and that the extensive year-round dissemination of virulent polioviruses requires a different strategy of vaccination from that used in the temperate-climate countries. The special point about the annual mass vaccinations with OPV for all children younger than three, four, or five years of age-which have proven highly successful in Cuba (for the past 20 years), in Brazil (during the past three years), and recently also in Mexico-is that all the children are usually vaccinated within one or two days, which quickly breaks the chain of transmission of the virulent viruses, and the annual campaigns create and maintain the maximum number of children with resistant intestinal tracts.