Figure 3 Probability to remain exacerbation‐free from month 0 to month 12 estimated by the Kaplan‐Meier method. The curves analysed by the log rank test were significantly different (p<0.0001; hazard ratio azithromycin v placebo 0.37 (95% CI 0.22 to 0.63)). At month 12 the mean (SD) probability to remain exacerbation‐free was 34.5 (7.9)% in the azithromycin group and 5.3 (3.6)% in the placebo group. This difference was also observed in the subpopulations of patients not infected or infected with P aeruginosa.