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 .
Objectives To assess the overall effect of vitamin D supplementation on  risk of acute respiratory tract infection  , and to identify factors modifying this effect .
High‐Dose Monthly Vitamin D for Prevention of Acute Respiratory Infection in Older Long‐Term Care Residents: A Randomized Clinical Trial
OBJECTIVES To determine the efficacy and safety of high-dose vitamin D supplementation for prevention of acute respiratory infection ( ARI ) in older long-term care residents . DESIGN R and omized controlled trial investigating high-dose vs st and ard-dose vitamin D from 2010 to 2014 . SETTING Colorado long-term care facilities . PARTICIPANTS Long-term care residents aged 60 and older ( n = 107 ) . INTERVENTION The high-dose group received monthly supplement of vitamin D3 100,000 IU , the st and ard-dose group received a monthly placebo ( for participants taking 400 - 1,000 IU/d as part of usual care ) or a monthly supplement of 12,000 IU of vitamin D3 ( for participants taking < 400 IU/d as part of usual care ) . MEASUREMENTS The primary outcome was incidence of ARI during the 12-month intervention . Secondary outcomes were falls and fractures , 25-hydroxyvitamin D levels , hypercalcemia , and kidney stones . RESULTS Participants ( 55 high dose , 52 st and ard dose ) were r and omized and included in the final analysis . The high-dose group had 0.67 ARIs per person-year and the st and ard-dose group had 1.11 ( incidence rate ratio ( IRR ) = 0.60 , 95 % confidence interval ( CI ) = 0.38 - 0.94 , P = .02 ) . Falls were more common in the high-dose group ( 1.47 per person-year vs 0.63 in st and ard-dose group ; IRR = 2.33 , 95 % CI = 1.49 - 3.63 , P < .001 ) . Fractures were uncommon and similar in both groups ( high dose 0.10 vs st and ard dose 0.19 per person-year ; P = .31 ) . Mean trough 25-hydroxyvitamin D levels during the trial were 32 . ng/mL in the high-dose group and 25.1 ng/mL in the st and ard-dose group . There was no hypercalcemia or kidney stones in either group . CONCLUSION Monthly high-dose vitamin D3 supplementation reduced the incidence of ARI in older long-term care residents but was associated with a higher rate of falls without an increase in fractures
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 .
Objectives To assess the overall effect of vitamin D supplementation on  risk of acute respiratory tract infection  , and to identify factors modifying this effect .