Vaccine-associated paralytic poliomyelitis in Brazil, 1989-1995

At the present time, the only poliovirus-caused poliomyelitis cases reported in Brazil and other countries of the Americas are of vaccine etiology. It is important for epidemiological surveillance and immunization programs to evaluate the epidemiological profile of cases of vaccine-associated paralytic poliomyelitis (VAPP) in order to establish criteria for case definition and vaccination strategies. To research VAPP in Brazil, 30 cases diagnosed and classified as such by the Ministry of Health between 1989 and 1995 were submitted to a descriptive study of clinical, laboratory, and epidemiological data. In addition, the risk of occurrence of VAPP was estimated in relation to determinants based on a cohort of 3,656 persons with acute flaccid paralysis. Among individuals who had received oral polio vaccine (OPV) from 4 to 40 days before the onset of paralysis, we found a relative risk of 8.88 (95% CI: 4.37-18.03) for VAPP as compared with persons who had not been vaccinated during the same time interval. For individuals who developed VAPP in the period following national vaccination days, the estimated relative risk was 2.94 (95% CI: 1.44-6.00). For the first dose of OPV administered to the general population the estimated risk was 1 case of VAPP for every 2.39 million doses; for total doses of OPV the risk was 1 case in 13.03 million doses. A major share of VAPP cases were related to children affected by prodromes (fever and gastrointestinal signs and/or symptoms), isolation of vaccine poliovirus type 2, paralysis of the lower limbs, and a mean age of 1 year.