Table 2. VDKA Trial Outcomes and Serious Adverse Events for Vitamin D₃ Supplementation vs Placebo.

Measure	Vitamin D3		Placebo		Group difference (95% CI)	Adjusted analysis
	No.	Mean	No.	Mean		Parameter estimate (95% CI)	P value
Primary outcome
Days to a severe exacerbationa	96	240	96	253	−13.1 (−42.6 to 16.4)	1.13 (0.69 to 1.85)b	.63
Secondary outcomes
Days to viral-induced severe exacerbationc	82	272	83	281	−9.1 (−35.5 to 17.2)	1.32 (0.63 to 2.75)b	.46
Proportion of participants in whom fluticasone dose was halved, No. (%)	91	28 (30.8)	91	29 (31.9)	−1.1 (−14.6 to 12.4)	0.99 (0.66 to 1.52)d	.99
Cumulative fluticasone dose, mg	96	59.6	96	55.2	4.41 (−0.99 to 9.80)	4.40 (0.001 to 8.80)e	.049
Exploratory outcomes
No. of severe exacerbations	96	0.58f	96	0.51f	0.07 (−0.14 to 0.28)	0.13 (−0.25 to 0.52)e	.50
No. of viral-induced severe exacerbations	86	0.26f	85	0.22f	0.03 (−0.11 to 0.18)	0.18 (−0.44 to 0.81)g	.56
Serious adverse eventsh
Participants with ≥1 serious adverse events, No. (%)	96	9 (9.4)	96	7 (7.3)
Total No. of serious adverse eventsi	96	11	96	9
Hospitalizations for asthma exacerbation, No.	96	8	96	6

Abbreviation: VDKA, Vitamin D to Prevent Severe Asthma Exacerbations.

^aDefined as a hospitalization or emergency department visit for asthma requiring systemic corticosteroids, or an asthma exacerbation leading to use of systemic corticosteroids (tablets, suspension, or injection) for at least 3 days.

^bHazard ratio stratified by site, sex, and race/ethnicity.

^cDefined as a nasal blow, collected within 7 days of the exacerbation, in which at least 1 virus was detected by polymerase chain reaction in a panel of common respiratory viruses (average, approximately 95% sensitivity and 99% specificity).

^dRelative risk ratio adjusted for sex, race/ethnicity, and days of follow-up in the study (model failed to converge when site included as covariate).

^eParameter estimate (beta coefficient, or adjusted difference in means) from Poisson regression adjusted for study site, sex, race/ethnicity, and days of follow-up in the study.

^fMean number of exacerbations per participant.

^gParameter estimate (beta coefficient, or adjusted difference in means) from Poisson regression adjusted for sex, race/ethnicity, and days of follow-up in the study (model failed to converge when site included as covariate).

^hSerious adverse events reported as comparative frequencies alone; sample size not sufficient to allow meaningful statistical comparisons.

ⁱSerious adverse events included hospitalizations (9 in each group), eosinophilia (1), and severe neutropenia (1). There were no instances of hypercalcemia in either group.