Smallpox eradication in Brazil, 1967-69.

The Campanha de Erradicacão da Varéola (CEV) was established in 1966 by the Brazilian Ministry of Health to eradicate smallpox. By October 1970 more than 75 million people had been vaccinated through this programme of systematic vaccination. In the 12 states where the attack phase had been completed by June 1969, there was an 80% decrease in reported cases in 1969 compared with the previous year. This decline in incidence contrasts sharply with the 99% increase in cases recorded in the other 15 states due to the increased level of surveillance.In 1969, 74% of cases occurred in persons under 15 years of age, while almost 93% of the persons infected were less than 30 years of age. The annual case-fatality rate, which has varied from 0.5% to 3.3% since 1956, indicates the disease to be variola minor. This has been confirmed by laboratory study.Careful investigation of reported cases has shown that in past years case reporting has been at a very low level, about 2.5% of the actual incidence.Data from epidemiological investigations of 22 outbreaks comprising more than 2000 cases and contacts indicate that the efficacy of smallpox vaccination was approximately 94%.