RT Journal Article SR Electronic T1 Double-blind randomised controlled trial of vitamin D3 supplementation for the prevention of acute respiratory infection in older adults and their carers (ViDiFlu) JF Thorax JO Thorax FD BMJ Publishing Group Ltd and British Thoracic Society SP 953 OP 960 DO 10.1136/thoraxjnl-2015-206996 VO 70 IS 10 A1 Adrian R Martineau A1 Yasmeen Hanifa A1 Karolina D Witt A1 Neil C Barnes A1 Richard L Hooper A1 Mital Patel A1 Natasha Stevens A1 Zinat Enayat A1 Zuhur Balayah A1 Asmat Syed A1 Aishah Knight A1 David A Jolliffe A1 Claire L Greiller A1 David McLaughlin A1 Timothy R Venton A1 Marion Rowe A1 Peter M Timms A1 Duncan Clark A1 Zia Sadique A1 Sandra M Eldridge A1 Christopher J Griffiths YR 2015 UL http://thorax.bmj.com/content/70/10/953.abstract AB Rationale Low-dose vitamin D supplementation is already recommended in older adults for prevention of fractures and falls, but clinical trials investigating whether higher doses could provide additional protection against acute respiratory infection (ARI) are lacking.Objective To conduct a clinical trial of high-dose versus low-dose vitamin D3 supplementation for ARI prevention in residents of sheltered-accommodation housing blocks (‘schemes’) and their carers in London, UK.Measurements and methods Fifty-four schemes (137 individual participants) were allocated to the active intervention (vitamin D3 2.4 mg once every 2 months +10 μg daily for residents, 3 mg once every 2 months for carers), and 54 schemes with 103 participants were allocated to control (placebo once every 2 months +vitamin D3 10 μg daily for residents, placebo once every 2 months for carers) for 1 year. Primary outcome was time to first ARI; secondary outcomes included time to first upper/lower respiratory infection (URI/LRI, analysed separately), and symptom duration.Main results Inadequate vitamin D status was common at baseline: 220/240 (92%) participants had serum 25(OH)D concentration <75 nmol/L. The active intervention did not influence time to first ARI (adjusted HR (aHR) 1.18, 95% CI 0.80 to 1.74, p=0.42). When URI and LRI were analysed separately, allocation to the active intervention was associated with increased risk of URI (aHR 1.48, 95% CI 1.02 to 2.16, p=0.039) and increased duration of URI symptoms (median 7.0 vs 5.0 days for active vs control, adjusted ratio of geometric means 1.34, 95% CI 1.09 to 1.65, p=0.005), but not with altered risk or duration of LRI.Conclusions Addition of intermittent bolus-dose vitamin D3 supplementation to a daily low-dose regimen did not influence risk of ARI in older adults and their carers, but was associated with increased risk and duration of URI.Trial registration number clinicaltrials.gov NCT01069874.