Vitamin D vs The Flu Vaccine - Is There A Stand-Out Winner?

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With the government promoting the flu vaccine and pharmacies offering it for the price of an entree at a restaurant, is there evidence for using the flu vaccination for flu prevention? And is there similar evidence available for humble vitamin D, a known immune modulator? 

A 2014 Cochrane review analysed the efficacy of flu vaccinations. It incorporated a huge amount of data including clinical trials with over 70,000 people, of which 27 were comparative cohort studies (with about 8 million people) and 20 were case-control studies (of nearly 25,000 people). A stand-out fact from this Cochrane review was that 71 people would need to be vaccinated to prevent one case of influenza. This statistic translates to a 1.4% response rate.[1]

In contrast, a 2010 study of 334 school-aged children found that, compared to placebo, 1200IU a day of vitamin D over 4 months achieved a risk reduction of 7.8% against the flu virus.[2] Also, like the flu vaccination, vitamin D can be used prophylactically.[3]

The results of these two studies suggests that vitamin D may be almost 6 times more effective at preventing influenza than vaccination.

Interestingly too, evidence shows that those with lower vitamin D levels in the winter months are more likely to get influenza.[4]

In order to obtain a more accurate comparison between the efficacy of the flu vaccine and vitamin D supplementation, a randomised, placebo-controlled clinical trial comparing the two interventions directly would be ideal. 

But once someone’s got the flu what can you do? Is there evidence for vitamin D once you are sick? In cases of active influenza, some practitioners have suggested “a vitamin D hammer” - a one-time dose of 50,000IU of vitamin D or 10,000IU three times daily for 2-3 days. With both of these dosages, a full resolution of all symptoms were achieved in 2-3 days with vitamin D alone.[3]

Sometimes supplementation can be expensive and it could be a barrier for at-risk populations, like the elderly, who may have less dispensable income. However, vitamin D can be a cost effective option to use as a viable flu vaccine alternative, with some products costing as low as 80c per 1000IU dose. 

Alternatively, the Medical Journal of Australia released a position statement in 2012 recommending between 7-40 minutes daily of sun exposure for fair skinned persons during the winter months so that vitamin D levels don’t drop too low.[5]


  1. Demicheli V, Jefferson T, Al-Ansary LA, et al. Vaccines to prevent influenza in healthy adults (review). Cochrane Database of Systematic Reviews 2014;Issue 3. [Full text]
  2. Urashima M, Segawa T, Okazaki M, et al. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Am J Clin Nutr 2010;91(5):1255-1260. [Full text]  
  3. Schwalfenberg G. Vitamin D for influenza. Can Fam Physician 2015;61(6):507. [Full text]
  4. Berry DJ, Hesketh K, Power C, et al. Vitamin D status has a linear association with seasonal infections and lung function in British adults. Br J Nutr 2011;106(9):1433-1440. [Abstract]
  5. Nowson C, McGrath J, Ebeling P, et al. Vitamin D and health in adults in Australia and New Zealand: a position statement. Med J Aust 2012;196(11):686-687. [Abstract]


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Sonya Reynolds

Sonya is a Nutritionist, with over 10 years industry experience. Sonya has held a variety of roles throughout her career including sales, customer service and practitioner educator roles for one of Australia's largest supplement companies whilst also running her clinic in Newtown, Sydney. Sonya has a strong interest in the areas of detoxification, gastrointestinal and digestive disorders and working with children with special health needs.