Intradermal hepatitis B virus immunization: immunogenicity and reactogenicity.

Mass immunization of hepatitis B virus (HBV) vaccine in adults is frequently demanded. However the high cost of conventional immunization is an obstacle to the provision of this vaccine. We investigated the serological response and adverse reactions following administration of a low-dose (1 or 2 micrograms of yeast-derived HBV vaccine (HB-VAX II, Merck, Sharp and Dohme) intradermally in young adults. Each 1 ml dose of the vaccine contained 10 micrograms of HBsAg protein. The study population included 58 female volunteers, aged 20-33 years, who were serologically-negative for HBV. They were alternately allocated to 1 microgram or 2 micrograms intradermal dose given by 2 experienced nurses as one or two 0.1 ml injections. Doses were given at 0, 1, and 6 months. Anti-HBs concentration was tested by enzyme-immunoassay on their sera obtained at 1, 6, and 7 months after the first dose. Positive seroconversion (anti-HBs greater than 10 IU/1) at 7 months was found in 90% (95% CL 79%, 100%) of the 1 microgram group and 96% (95% CL 89%, 100%) of the 2 micrograms group. Local reaction, a transient pigmented macule with an underlying nodule, was found in most volunteers but did not bother them. Intradermal HBV immunization could be an alternative strategy for mass immunization in young adults.