Intradermal hepatitis B immunization with yeast-derived vaccine: serological response by sex and age.

The efficacy and acceptability of yeast-derived recombinant hepatitis B vaccine given by the intradermal route was investigated in 221 health care volunteers. Two hundred and sixteen received a full course of three doses of vaccine. Only one subject was withdrawn because of a significant adverse reaction (psoriasis). The vaccine stimulated an antibody response in 81%. The response to the vaccine was better in women than in men (87% compared with 71%, p = 0.007) and in women below the age of 40 years compared with older women (94% compared with 76%, p = 0.01). For men the response showed a sequential decline with age for each decade (90% responders from age 29 or less, 72% aged 30-39 and 65% aged 40 or more, p = 0.04). Retrospective enquiry showed that over 90% had found the intradermal route acceptable and 59% would prefer vaccine by the intradermal route in preference to intramuscular notwithstanding local reactions. Although the seroconversion rate was of a high order in younger women the antibody titres were not high with only 9 of 215 recipients developing titres greater than 1000 mIU/ml, a level which could be expected to ensure prolonged immunity. A fourth intradermal dose of vaccine given to 60 volunteers who had shown a low response (less than 38 mIU/ml) or no serological response to a three-dose course stimulated a good booster effect (to 150-600 mIU/ml) in only 5 (8%).