RESUMEN
This study was made as part of the Surveillance Program that has been implemented for 10 years for the perinatal control of hepatitis B in children of positive mothers. The control of hepatitis B is possible thanks to the existance of the vaccines against this entity. In Cuba, there is a safe and effective vaccine for its prevention. The perinatal infection risk among children of mothers positive to hepatitis B surface antigen (HbsAg) is high. Many of these infections may be prevented if mothers positive to HbsAg are early detected and their children are vaccinated at birth. 121 serum samples from positive mothers and their respective 7-month-old children from all over the country that were received at the National Viral Hepatitis Reference Laboratory of "Pedro Kouri" Tropical Medicine Institute were studied from September to December, 2000. All the samples underwent the test to detect HbsAg and anti-HBs antibodies were investigated in children negative to HbsAg. 100% of positivity to HBsAg was found among mothers. 5.7% of positivity to this antigen was obtained in children. In negative children the seroprotection attained in this group was 94.7% with an anti-HBs Geometric Mean Titer (GMT) of 233.3 UI/L. The normoresponsive children predominated with 52.6%. The Efficacy Index of the vaccine used ranged from 95.9% to 99.3%.