Since the emergence of the novel coronavirus SARS-CoV-2 late last year, the human immune system has been faced with a significant new challenge. The human immune system relies on a multitude of factors to mount an effective response against viral threats in order to safeguard the body’s physiological state. It has long been known that vitamin supplementation goes hand to hand with improved host immunity, providing protection against viral infections.
In this Original Research article in The FEBS Journal, Merzon et al  set out to identify whether vitamin D deficiency was a risk factor for COVID-19 infection and hospitalization in a pool of 7,807 individuals. To this end, authors used blood plasma measurements of 25(OH)D, an inactive intermediate metabolite of vitamin D, from one of the largest curated up-to-date Israeli patient databases between February 1st to April 30th. The authors of this study investigated records for 782 individuals who had tested positive for COVID-19 and found that the mean concentration of 25(OH)D in their blood plasma had been significantly lower than that of individuals who had tested negative for COVID-19 (19 vs 20.55 ng/ml, respectively). According to this study, having a concentration of this vitamin D precursor, 25(OH)D, under 20 ng/ml is classed as a vitamin D deficiency.
Additionally, Merzon et al established a significant association between low 25(OH)D levels and likelihood of SARS-COV-2 infection (adjusted odds ratio 1.5, 95% CI 1.13-1.98, p<0.001), independent of demographic variables and other health conditions (such as dementia or cardiovascular disease). An odds ratio of 1.5 means that individuals with a vitamin D deficiency are 50% more likely to be diagnosed with COVID-19 than those with >20 ng/ml of the vitamin D precursor in their blood plasma.
Merzon et al found a trend in their data supporting a low mean concentration of blood plasma 25(OH)D was associated with an increased likelihood of hospitalization due to a COVID-19 infection. However, this trend was not significant when other factors were taken into account in a multivariate analysis, meaning that such a conclusion could not be supported based on their population sample. Notably, of the people diagnosed with SARS-COV-2 infection, individuals aged 50 or over had a statistically higher likelihood to be hospitalised (adjusted odds ratio 2.71). Among them, individuals were more likely to be male and to come from a low to medium socioeconomic status.
Collectively, Merzon et al analysed population data from 7,807 individuals during an ongoing pandemic and established that the association between vitamin D deficiency and viral infection susceptibility holds true for COVID-19, contrary to similar studies with smaller sample sizes. Moreover, they were able to tease out that individuals at the age of 50 or higher had a statistically higher likelihood to be hospitalised, in support of other studies indicating that the severity of infection increases with age. The implications of this work could spread further than the academic community, with bearings for the clinical setting and policymaking of public health guidelines.
The Original Research article can be read in full in The FEBS Journal: https://febs.onlinelibrary.wiley.com/doi/abs/10.1111/febs.15495
- Merzon, E., Tworowski, D., Gorohovski, A., Vinker, S., Golan Cohen, A., Green, I. & Frenkel Morgenstern, M. (2020) Low plasma 25(OH) vitamin D level is associated with increased risk of COVID-19 infection: an Israeli population-based study, The FEBS Journal. n/a.