[M T]

Here's another study, pre-COVID-19 but on acute respiratory infections, from BMJ in 2017 about the effect of Vitamin D supplementation.

Design Systematic review and meta-analysis of individual participant data (IPD) from randomised controlled trials.



Conclusions Vitamin D supplementation was safe and it protected against acute respiratory tract infection overall. Patients who were very vitamin D deficient and those not receiving bolus doses experienced the most benefit.



[*]Meta-analysis of IPD from 10 933 participants in 25 randomised controlled trials showed an overall protective effect of vitamin D supplementation against acute respiratory tract infection (number needed to treat (NNT)=33)
[*]Benefit was greater in those receiving daily or weekly vitamin D without additional bolus doses (NNT=20), and the protective effects against acute respiratory tract infection in this group were strongest in those with profound vitamin D deficiency at baseline (NNT=4)

[M T]

Here's another study, pre-COVID-19 but on acute respiratory infections, from BMJ in 2017 about the effect of Vitamin D supplementation.

Design Systematic review and meta-analysis of individual participant data (IPD) from randomised controlled trials.



Conclusions Vitamin D supplementation was safe and it protected against acute respiratory tract infection overall. Patients who were very vitamin D deficient and those not receiving bolus doses experienced the most benefit.



[*]Meta-analysis of IPD from 10 933 participants in 25 randomised controlled trials showed an overall protective effect of vitamin D supplementation against acute respiratory tract infection (number needed to treat (NNT)=33)
[*]Benefit was greater in those receiving daily or weekly vitamin D without additional bolus doses (NNT=20), and the protective effects against acute respiratory tract infection in this group were strongest in those with profound vitamin D deficiency at baseline (NNT=4)