Vitamin D is of proven benefit in

preventing respiratory tract infections.

The NNT (Number Needed to Treat )  

showed that NNT to prevent one

episode of  'flu for very deficient

patients was 4 compared to 40

for the flu vaccine! Vitamin D is

ten times more effective

than vaccination.

Vitamin D supplementation to prevent

acute respiratory tract infections:

systematic review and meta-analysis

of individual participant data


Adrian R Martineau, professor of

respiratory infection and immunity

Centre for Primary Care and Public Health,

Blizard Institute, Barts and

The London School of Medicine and Dentistry,

Queen Mary University of London,

London E1 2AB, UK

Asthma UK Centre for Applied Research,

Blizard Institute, Queen Mary University of

London, London, UK

Other Authors:

David A Jolliffe, postdoctoral research fellow  

Richard L Hooper, reader in medical statistics 

Lauren Greenberg, medical statistician

John F Aloia, professor of medicine  

Peter Bergman, associate professor 

Gal Dubnov-Raz, consultant paediatrician 

Susanna Esposito, professor of paediatrics  

Davaasambuu Ganmaa, assistant professor  

Adit A Ginde, professor of emergency medicine  

Emma C Goodall, assistant professor

Cameron C Grant, associate professor 

Christopher J Griffiths, professor of primary care  

Wim Janssens, professor of pneumonology  

Ilkka Laaksi, chief administrative medical officer  

Semira Manaseki-Holland, senior clinical lecturer  

David Mauger, professor of public health sciences and statistics  

David R Murdoch, professor of pathology

Rachel Neale, associate professor

Judy R Rees, assistant professor

Steve Simpson Jr, postdoctoral research fellow

Iwona Stelmach, professor of paediatric allergy 

Geeta Trilok Kumar, associate professor

Mitsuyoshi Urashima, professor of molecular epidemiology

Carlos A Camargo Jr, professor of emergency medicine, medicine, and epidemiology


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To assess the overall effect of vitamin D supplementation on risk of acute respiratory tract infection, and to identify factors modifying this effect.



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

Data sources 


Medline, Embase, the Cochrane Central Register of Controlled Trials, Web of Science,, and the International Standard Randomised Controlled Trials Number registry from inception to December 2015.

Eligibility criteria for study selection 


Randomised, double blind, placebo controlled trials of supplementation with vitamin D3 or vitamin D2 of any duration were eligible for inclusion if they had been approved by a research ethics committee and if data on incidence of acute respiratory tract infection were collected prospectively and prespecified as an efficacy outcome.



25 eligible randomised controlled trials (total 11 321 participants, aged 0 to 95 years) were identified. IPD were obtained for 10 933 (96.6%) participants. Vitamin D supplementation reduced the risk of acute respiratory tract infection among all participants (adjusted odds ratio 0.88, 95% confidence interval 0.81 to 0.96; P for heterogeneity <0.001). In subgroup analysis, protective effects were seen in those receiving daily or weekly vitamin D without additional bolus doses (adjusted odds ratio 0.81, 0.72 to 0.91) but not in those receiving one or more bolus doses (adjusted odds ratio 0.97, 0.86 to 1.10; P for interaction=0.05). Among those receiving daily or weekly vitamin D, protective effects were stronger in those with baseline 25-hydroxyvitamin D levels <25 nmol/L (adjusted odds ratio 0.30, 0.17 to 0.53) than in those with baseline 25-hydroxyvitamin D levels ≥25 nmol/L (adjusted odds ratio 0.75, 0.60 to 0.95; P for interaction=0.006). Vitamin D did not influence the proportion of participants experiencing at least one serious adverse event (adjusted odds ratio 0.98, 0.80 to 1.20, P=0.83). The body of evidence contributing to these analyses was assessed as being of high quality.



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.


Systematic review registration 


PROSPERO CRD42014013953.