Important epidemiological aspects of poliomyelitis in the city of S. Paulo, Brazil

Abstract

Several epidemiological aspects of poliomyelitis in the city of S. Paulo (Brazil) are discussed and related to measures that must be taken to maintain control of this disease. Results show the need of continued vaccination of the whole infant population, because a decrease in vaccination may permit an upraise of the disease. During four years of tight control, 58 new cases were registered per year. After that, in 1971, 195 cases appeared. Only in the second half of 1975, when immunization programs were again improved, was the situation controlled. This study shows that poliomyelitis still acts in the classical mode in that about 75% of the cases occur in children two years old or under. This, plus evidence that type 1 poliovirus is the type prevalent in S. Paulo, strengthens the idea that the epidemiology of this viral illness has not been essentially changed by the vaccination programs. Another finding is that the Sabin vaccine has been less efficient in our environment than in developed countries with temperate climates. This is due to epidemiological factors and operational conditions. In 1970-1977, 8.9% of the cases had received three, four, or more doses of the trivalent oral vaccine, and 43.3% had received at least one dose of the oral vaccine. The recommendation is herewith made that the number of doses of the basic series for immunization against poliomyelitis be increased from three to five in order to counterbalance mishaps in the act of oral vaccination and our environment's difficulties related with the epidemiology of the disease.