Annual rates of respiratory events by treatment group. Data are shown in a Tukey box plot. The horizontal line in the box represents the median. The bottom and top of the box indicate the first and third quartiles; the upper whisker shows the largest value from the top of the box that is no further than 1.5 times the interquartile range (IQR), the lower whisker shows the smallest value from the bottom of the box to within 1.5 times the IQR, and data beyond the ends of the whiskers are displayed as points. The mean (♦; ± standard error of the mean [SEM]) annual rates of respiratory events at baseline, intervention year 1, and intervention year 2 were 3.91 ± 0.35, 3.34 ± 0.37, and 1.54 ± 0.37 and 4.34 ± 0.35, 4.28 ± 0.36, and 1.49 ± 0.37, respectively, for monthly standard-dose and high-dose oral vitamin D3. The rates did not differ significantly between the groups (P = .24), but they decreased significantly during year 2 in both groups (P = .0005).