FIG. 3.

Humoral immune response (IgG) to C. burnetii antigens at various times after booster vaccination with CMRI (expressed as 2ⁿ). Mean geometric antibody titers to NMIS, CMRI, and NMISR after a 30-μg (open diamonds, open squares, and open triangles, respectively) or 60-μg (closed diamonds, closed squares, and closed triangles, respectively) primary dose and 30-μg boost were measured before boosting and 7, 14, 21, 28, and 42 days after boosting. Anti-CMRI mean titers measured 14 and 21 days after boosting (30-μg primary dose) were significantly (P < 0.05) elevated from baseline titers. Anti-NMISR mean titers measured 7, 14, 21, 28, and 42 days after boosting (30-μg primary dose) were significantly (P < 0.05) elevated from baseline titers. Anti-NMIS mean titers measured after boosting (30-μg primary dose) were not significantly (P ≥ 0.05) elevated from baseline titers. All mean titers (anti-NMIS, anti-CMRI, and anti-NMISR) measured 14, 21, 28, and 42 days after a 60-μg primary CMRI dose and boosting were significantly elevated (P < 0.05) compared to corresponding baseline (day 0) titers.