Vitamin D supplementation to prevent acute respiratory infections: individual participant data meta-analysis.

Study answer

What this study found

Vitamin D supplementation reduces ARI risk; overall reduction in the proportion of participants with at least one ARI (adjusted OR 0.88; 95% CI 0.81 to 0.96; NNT 33). ARI rate also reduced (adjusted IRR 0.96; 95% CI 0.92 to 0.997). Time to first ARI not significantly affected (adjusted HR 0.95; 95% CI 0.89 to 1.01). Stronger protection in those with baseline 25(OH)D < 25 nmol/L (adjusted OR 0.58; 95% CI 0.40 to 0.82; NNT 8). Daily or weekly regimens without bolus doses showed protection (adjusted OR 0.81; 95% CI 0.72 to 0.91; NNT 20); bolus dosing did not (adjusted OR 0.97; 95% CI 0.86 to…

Study & population

Design: randomized, double-blind, placebo-controlled trials of vitamin D supplementation; Participants: birth to 95 years, both sexes, varied health status; trials conducted in 15 countries.

Intervention

Oral vitamin D3 supplementation; regimens included daily dosing, weekly dosing, monthly to quarterly bolus dosing (bolus doses of at least 30,000 IU), and combinations of bolus and daily dosing; durations ranged from 7 weeks to 1.5 years.

Key limitation

Power limited for some subgroups (e.g., very low baseline 25(OH)D with bolus dosing); adherence data not available for all participants; heterogeneity in dosing regimens and baseline vitamin D status; ARI definitions varied and virological confirmation limited; potential small-study bias suggested by funnel plot.

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Original abstract