Initial clinical and immunologic evaluation of a new phase I Q fever vaccine and skin test in humans.

A new phase I Q fever skin test was administered to 74 subjects. Thirty-eight had less than 8 mm and 36 had greater than or equal to 10 mm erythema at 24 hr. Only 14 had circulating antibody. Three skin test-positive and 17 skin test-negative, seronegative individuals subsequently received 6 or 30 micrograms of vaccine in a single dose. All skin test-positive individuals and one skin test-negative individual developed mild local reactions. Seventeen of 18 recipients developed fluorescent antibody to phase II antigen, and five developed positive phase II complement fixation titers. Serial assays of specific lymphocyte proliferation (LT) performed in 15 individuals revealed an increase in phase II LT in nine and an increase in phase I LT in six. All local reactions occurred in individuals with preexisting phase II LT. On the basis of these results, this vaccine and skin-test preparation appear safe, effective, and promising for eventual use in at-risk personnel.