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Table 2 Frequency, severity, duration and viral load (log viral copies/mL) associated with URTI according to vitamin D allocation

From: Vitamin D3and gargling for the prevention of upper respiratory tract infections: a randomized controlled trial

Outcome measure Clinical URTI Laboratory confirmed URTI
Vitamin D (n = 258) Placebo (n = 234) Effect measure (95% CI) P value Vitamin D (n = 256) Placebo (n = 233) Effect measure (95% CI) P value
Imputed URTI episodes, No. (%) 91 (30.3) 114 (38.0) *RR:0.80 (0.63-1.02) 0.08     
Complete case URTI episodes, No. (%) 70 (27.1) 80 (34.2) *RR:0.79 (0.61-1.03) 0.09 26 (10.2) 44 (18.9) *RR:0.54 (0.34-0.84) 0.007
Viral load, mean (SD)      5.51 (1.6) 6.40 (1.2)   0.036
Symptom duration, mean days, (SD) 6.0 (1.6) 6.2 (1.3) *HR: 1.32 (0.59-2.90) 0.49 5.8 (1.5) 6.2 (1.2) *HR: 1.30 (0.49-3.48) 0.59
Symptom severity, mean (SD) 218.6 (124.0) 199.8 (108.1)   0.41 229.7 (110.3) 181.5 (91.9)   0.09
  1. RR: relative risk, HR: Hazard ratio.
  2. *The Poisson and Cox regression models were adjusted exclusively for randomization strata: vitamin D allocation, gargling allocation, year of participation and type of housing.
  3. Viral load was measured as log10 viral copies/mL.
  4. Symptom duration and severity was measured only in participants who self-reported illness (ie. not for adjudicated events), n = 106. For clinical URTI, n = 53 in each of the vitamin D and placebo groups. For laboratory confirmed URTI n = 22 and n = 34 in the vitamin D and placebo groups respectively.