Intradermal hepatitis B vaccination in an abbreviated schedule

Two low-dose intradermal regimens for hepatitis B vaccination were compared with the standard 1 ml dose administered intramuscularly to healthy, 22-42 year old individuals. All regimens were administered in an abbreviated time schedule. Nineteen individuals (ID-1 group) received three 0.1 ml (2 μg) doses intradermally at times 0, 1 month and 4 months. Twenty-four individuals (ID-2 group) received two injections of 0.2 ml (4 μg) each intradermally at time 0 and one 0.1 ml (2 μg) injection 4 months later. Twenty individuals (IM group) received the recommended three 1.0 ml (20 μg) doses intramuscularly at times 0, 1 month, and 4 months. No significant adverse reactions were attributable to the intradermal administration of vaccine although the majority of vaccinees developed small areas of induration and hyperpigmentation at the injection site that persisted for several months. One month following the last injection, all vaccinees had developed anti-HBsAg antibodies. One hundred percent of ID-1 and IM vaccinees and 95% of ID-2 vaccinees had protective levels of antibody (≥10 mIU ml^-1). The geometric mean titre (GMT) for the IM group (2692 mIU ml^-1) was somewhat higher than for the ID-1 (1230 mIU ml^-I) and the ID-2 (851 mIU ml^-1) groups, but the differences were not statistically significant. Since anti-HBs antibodies are thought to confer protection against hepatitis B, these results suggest that a shortened regimen of intradermal vaccine may be effective in healthy adults. However, no efficacy study has yet been done with intradermal hepatitis B vaccine.