Takeaway
- This meta-analysis found a small but significant protective effect of vitamin D supplementation on the risk of having ≥1 acute respiratory infections (ARIs) vs placebo, but there was evidence of significant heterogeneity of effect across trials.
- Protection was associated with administration of daily doses of 400-1000 international units (IU) for up to 12 months and age at enrolment of 1.00-15.99 years.
Why this matters
- A 2017 meta-analysis of data from 25 randomised controlled trials (RCTs) of vitamin D supplementation for the prevention of ARIs showed a protective effect of this intervention.
- The relevance of these findings to COVID-19 is not known and requires further investigation.
Study design
- Meta-analysis of 43 RCTs including 49,419 participants.
- Funding: None.
Key results
- A significantly lower proportion of participants in the vitamin D supplementation group had ≥1 ARIs vs placebo group (61.3% vs 62.3%; OR, 0.92; 95% CI, 0.86-0.99; 37 studies; I²=35.6%; Pheterogeneity=.018).
- No significant effect of vitamin D supplementation on the risk of having ≥1 ARIs was seen for any of the subgroups defined by baseline 25(OH)D concentration.
- A significant protective effect of vitamin D supplementation was seen in trials in which vitamin D was given (OR; 95% CI):
- in a daily dosing regimen (0.78; 0.65-0.94; 19 studies; I²=53.5%, Pheterogeneity=.003);
- at daily dose equivalents of 400-1000 IU (0.70; 0.55-0.89; 10 studies; I²=31.2%, Pheterogeneity=.16);
- for a duration of ≤12 months (0.82; 0.72-0.93; 29 studies; I²=38.1%; Pheterogeneity=.021); and
- to participants aged 1.00-15.99 years at enrolment (0.71; 0.57-0.90; 15 studies; I²=46.0%; Pheterogeneity=.027).
- No significant interaction was seen between allocation to the vitamin D
supplementation group vs the placebo group and dose, dose frequency, study duration, or age.
Limitations
- Heterogeneity across trials.
- Risk of bias.
This clinical summary originally appeared on Univadis, part of the Medscape Professional Network.