Low dose hepatitis B vaccination in children.

One hundred and sixty-nine children negative for hepatitis B surface antigen (HBsAg) and antibody (anti-HBs), were given three doses of hepatitis B vaccine at monthly intervals. Doses were two micrograms or four micrograms given intradermally (ID) or intramuscularly (IM). All children were tested for HBsAg, anti-HBs and antibody to hepatitis B core antigen (anti-HBc) one month after the second dose of vaccine. Overall, 74% of children on two micrograms doses and 71% of children on four micrograms doses responded to two doses of vaccine by the production of anti-HBs. At this point, mass immunisation of other susceptible children was commenced. Four of 92 (4%) three to five year old subjects and 20 of 77 (26%) nine to 12 year olds were found to be anti-HBc positive alone, indicating prior infection. All 77 older children were further tested two months after the third dose of vaccine. All 20 who were anti-HBc positive, sero-converted for anti-HBs. Of the remaining 57, 52 (91%) produced anti-HBs at acceptable geometric mean titres (GMT). Three doses of two micrograms of H-B-VAX, given at monthly intervals were chosen for mass vaccination of high risk susceptible children in this mobile community, providing over 90% sero-conversion at low cost with a minimum of side effects.