The prevention of
hepatitis B by vaccination is one of the most efficient tools to avoid the transmission of the virus. This study evaluated the immunogenicity of the national
vaccine Butang in children born in Campo Mourão City, state of Paraná, Brazil, aged 7 to 12 months, by determining the anti-
HBsAg antibodies levels after completion of the National Immunization Program Protocol for
hepatitis B. All 70 children evaluated by the MEIA method (immune-enzymatic micro particles) showed seroconversion to the Butang
vaccine. Nine children (12.9%) presented a low response, with anti-HBs titers between 11 and 100 mUI/ml; 39 children (55.7%) showed a good response to the
vaccine, with titers between 101 and 1000 mUI/ml; and 22 children (31.4%) showed
antibodies titers higher than 1000 mUI/ml. The mean titer of the anti-HBs antibody titers was 1408.1 +/- 2870.26 mUI/ml (15.7 to 19560.0 m UI/ml). The levels of
antibodies produced by the prematurely-born children were not statistically different from those found in the newborns. Fifty-five children were also evaluated through the ELFA method (ELISA with a final detection in fluorescence), which presented similar results. The results obtained in our study corroborated the effectiveness of the national
vaccine Butang in newborn children of Campo Mourão City, Paraná, even if they were premature.