HIGH-RATE OF SEROCONVERSION FOLLOWING ADMINISTRATION OF A SINGLE SUPPLEMENTARY DOSE OF RECOMBINANT HEPATITIS-B VACCINE IN IRANIAN HEALTHY NONRESPONDER NEONATES

Forty-nine Iranian neonates who failed to develop a protective anti he patitis B surface antigen (HBs) response following primary vaccination with triple doses of recombinant hepatitis B vaccine, were classified as hypo-responders (anti-HBs > 1 < 10 IU/1) or non-responders (anti-H Bs < 1 IU/1) and subsequently challenged with a single supplementary v accine dose. A protective and anamnestic type of response was observed in 90% (44/49) of the neonates. The mean titer of anti-HBs antibody w as significantly higher following supplementary vaccination, compared to that achieved after primary vaccination. This was more evident in t he primary hypo-responder neonates (P < 0.00001) than the non-responde r group (P < 0.002). The results indicate that a significant proportio n of the nonresponder neonates to HBs antigen can be induced to develo p a protective and long-lasting antibody response by administration of a single additional vaccine dose.