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.
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. Also, like the flu vaccination, vitamin D can be used prophylactically.
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.
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.
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.
- 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]
- 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]
- Schwalfenberg G. Vitamin D for influenza. Can Fam Physician 2015;61(6):507. [Full text]
- 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]
- 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]