The immunogenicity and safety of intradermal hepatitis B vaccine

Background. One of the chief barriers to a greater use of hepatitis B vaccine is the high cost of the vaccine itself. A number of small research trials have shown that an adequate immune response can be induced at a much lower cost by administering one tenth of the vaccine using an intradermal technique. The purpose of this study was to ascertain whether these results could be replicated in a larger clinical trial. Methods. Vaccine recipients included health care providers, police officers, and firefighters. Recipients were given 0.1 mL of plasma-derived hepatitis B vaccine intradermally on days 1, 30, and 180. Antibody response was measured on day 210, with seroconversion defined as a sample-to-negative (S/N) ratio of greater than or equal to 10. Any local and systemic side effects were documented. Results. Six hundred sixteen individuals completed the vaccination series, and seroconversion occurred in 534 (86.7%). The rate of seroconversion in those younger than 40 years was 91.2% and in those 40 years and older was 75.1%. The mean S/N ratio was 154.9 (range 0 to 620) and decreased with increasing age (r = -.25, P = .0001). Side effects were largely limited to local reactions. Conclusions. The results support the use of the intradermal technique as a cost-effective alternative to the intramuscular route in individuals younger than 40 years. The intradermal technique may be used in older individuals if titers are obtained to assure seroconversion. Because of the restricted availability of the plasma-derived vaccine used in this study, similar trials with recombinant vaccine should be undertaken.