The Influence of Phase on the Protective Potency of Q Fever Vaccine

Abstract

Summary: Q fever vaccines made from purified Coxiella burneti in phase I and tested in guinea pigs were shown to possess protective potencies 100 to 300 times greater than comparable phase II vaccines when the challenge rickettsiae were in phase I. Significant differences in vaccine potencies of Q fever vaccines made from different strains were explained on the basis of phase differences rather than strain differences. The relative potencies of phase I and phase II vaccines were shown to depend upon the phase of the challenge rickettsiae. Phase I antigen injected into guinea pigs convalescent from Q fever was shown to produce higher and more persistent levels of complement-fixing and agglutinating antibodies than phase II antigen. It was shown that the agglutination-resuspension test reflected accurately the immune state of vaccinated guinea pigs before challenge, whereas this was not true of the complement fixation test.