Poliomyelitis: Cuba, 1962-1978.

PIP: Before the Cuban Revolution in 1959, poliomyelitis was endoepidemic, with epidemic peaks every 5-7 years and subsiding peaks in the intervening intervals. 18 mass poliomyelitis vaccination campaigns have been conducted since 1962, and there have been only 6 notified cases. In each case, vaccine administration was preceded by a survey of the level of immunity to polio vriuses and the results of serologhic analyses were used to determine the age of vaccination and the type of vaccine used. Starting with the 9th campaign, trivalent vaccine has been administered in candy form in 2 doess to children 1 month-3 years and a booster is given at 9 years of age to reactivate immunity. Except for the 1st immunization campaign, when 98.6% coverage was achieved, coverage has exceeded 100%. The age group with the lowest prevalence of immunization has consistently been infant under 1 year of age. Serologic surveys indicate that the proportion of resistant individuals rises progressively with age. Resistance tends to level off, however, at 3 years of age, suggesting that once a give level of immunity is attained, it is dufficult to raise it. Protective antibody levels against the 3 polio viruses in persons over 14 years of age is estimated to be about 90%.^ieng