Estado imune contra o virus vacinal (17D) da febre amarela em duas populacoes do Estado da Bahia

The occurrence of cases of yellow fever (YF) and also the extensive distribution of A. aegypti in Brazil, inspired a study about the estimate of immunity against vacinal virus (17D) among the residents at two cities of the Bahia state, Ipupiara (n = 461) and Prado (n = 228). At this non-endemic area of YF, the search for serology antibody against 17D (Ab17D) and 18 another arbovirus was made thereby hemagglutination inhibition (HI). Only 1.2% (8/689) showed Ab17D, six of those with monotypic sort. The heterotypic sort for flavivirus (FLV) was interpreted as associated to immunity against 17D too, being much frequent in Prado (30.3%) than in Ipupiara (23.2%). The age ≥50 years and residence in another states were related to seropositive for FLV, the same way that vaccination's history (17D). However, the history of vaccination presented low percentages of sensibility (≤ 45.4%) and predictive-positive value (£38.4%), but high specificity (≥70.8%) and predictive-negative value (≥78.8%). Therefore, the frequency of residents with Ab17D was low (1.2%), although the higher frequency (25.5%) of antibody FLV carrier's, what signifies that 26.7% of the studied population should present protection against the YF virus.