SUBOPTIMAL RESPONSE FOLLOWING INTRADERMAL HEPATITIS-B VACCINE IN INFANTS

Two hundred and twenty-five infants were randomly assigned to receive 2 mu g of plasma-derived hepatitis B vaccine (Heptavax) intradermally (ID-2), 10 mu g intramuscularly (IM-10), or 2 mu g intramuscularly (IM-2) in the deltoid region at birth, 2 and 4 months. At 6 months, ID-2 infants were less likely to have developed greater than or equal to 10 mIU ml(-1) of antibody to hepatitis B surface antigen (anti-HBs) than IM-10 infants (91 versus 100%; p=0.02) and had a lower geometric mean concentration of anti-HBs (312 mIU ml(-1) versus 2248 mIU ml(-1); p<0.01). At 6 months IM-10 infants had significantly lower mean weights and lengths than infants receiving 2 mu g doses of vaccine. Intramuscular administration of 2 mu g and 10 mu g doses of Heptavax in the deltoid of young infants was well tolerated and effective; however, intradermal administration of Heptavax provided no immunological benefit over intramuscular administration and resulted in significantly higher rates of induration and persistent hyperpigmentation. Intramuscular immunization at birth, 2 and 4 months is an acceptable, effective alternative schedule for immunizing infants.