A review of literature published in the Journal of Molecular Science sought to examine the role of vitamin D as therapy or prevention against influenza came short of delivering definitive answers,
The survey of the literature concerning the role of vitamin D in the immune system and immunization, especially against influenza viruses, does not give an unequivocal and one-word answer of “yes” or “no” to the questions: “Does vitamin D supplementation enhance the host’s resistance to influenza?” and “Does vitamin D supplementation play a role in the therapy of viral infection diseases?”
However, the author takes the position that,
The studies clearly show that vitamin D is, undoubtedly, part of the complex factors which affect the immune response. So, assessing vitamin D status and maintaining optimal serum levels should be considered in all ageing adults and children, and micronutrients should be regarded as one of the essential factors which improve our health condition overall and also support our fight against diseases.
This was a review of literature and not a medical trial.
The aim of the paper was to present recent data on the possible role of vitamin D in modulating the immune response in influenza virus infection and its potential preventive and therapeutic potential in that disease.
Gruber-Bzura BM. Vitamin D and Influenza-Prevention or Therapy?. Int J Mol Sci. 2018;19(8):2419. Published 2018 Aug 16. doi:10.3390/ijms19082419