Intradermal immunization with reduced doses of human diploid cell strain rabies vaccine: evaluation of antibody response by ELISA and mixed hemadsorption test

The antibody response to the rabies human diploid cell strain vaccine was compared after pre-exposure immunization with 0.1 ml intradermal (i.d.) and 1.0 ml subcutaneous (s.c.) vaccination. After primary immunization, 2 doses of vaccine 1 month apart, all vaccinees in the two groups had antibody titers detectable by ELISA. However, the mean antibody titer after the 0.1 ml i.d. doses (5.9 EU/ml) was half of what was obtained after the 1.0 ml s.c. doses (12.2 EU/ml). Likewise, though all vaccinees responded on the 1-year booster dose the mean antibody level after i.d. vaccination (8 EU/ml) was 2.5 times lower than after 1.0 ml s.c. dose (21.5 EU/ml). At 1 year 70% of the vaccinees had detectable antibody levels irrespective of vaccination route. A few individuals responded to one of their i.d. doses with only minor titer rises which is supposed to be due to inadvertent s.c. injection of the i.d. dose.