Serologic and Skin-Test Response after Q Fever Vaccination by the Intracutaneous Route

Abstract

Results of intracutaneous injection of Q fever vaccine in man were compared with results previously obtained by subcutaneous injection. Antibody response was related to the number of doses of vaccine given but was more delayed and lower in titer than that obtained after subcutaneous injection. However, as measured by the radioisotope-precipitation test, a significant level of antibodies was attained in all groups in 40 weeks. Results of prevaccination skin tests were used as criteria for safety of vaccination. There was slow development of the skin-test reaction, and some tests which were negative 48 hr after injection were positive in 7 days. Volunteers with strong reactions were not vaccinated, but some persons with minimal reactions were vaccinated. There were no significant differences in antibody development in the skin-test weakly positive and skin-test negative vaccinated groups. The apparent absence of anamnestic antibody response cast doubt upon the significance of the minimal skin-test reactions. Eighty per cent of volunteers became skin-test positive after vaccination. Skin-test reactivity reached a maximum long after maximum antibody response as measured by the capillary-agglutination test. One reaction severe enough to be unpleasant but not disabling in any sense occurred unpredictably (Fig. 1). Other, minor, reactions resulting in obvious skin blemishes of long duration occurred more frequently. Those reactions as well as the more delayed and lower antibody response, make the intracutaneous route an undesirable one for injection of Q fever vaccine.