Rachel Nicoli and Michael Y. Henein

Seven meta-analyses and systematic reviews and three later clinical trials argued that low vitamin D status increased susceptibility to COVID-19 and the risk of greater disease severity and mortality [1–10]. Furthermore, there are five meta-analyses and systematic reviews of vitamin D supplementation for the prevention of acute respiratory infection (ARI) [11,12] and COVID-19 [13–15], as well as a later clinical trial [16], all showing that supplementation can protect against COVID-19 infection, disease severity, and death. The evidence could not be much more conclusive than this.

Consequently, it was surprising to learn about Joliffe et al.’s recent randomized con- trolled trial of vitamin D to prevent ARIs and COVID-19, which concluded that ‘Among people aged 16 years and older with suboptimal vitamin D status, implementation of a population level test-and-treat approach to vitamin D supplementation was not associated with a reduction in risk of all cause acute respiratory tract infection or COVID-19’

… Overall, this study by Joliffe et al., represents a wasted opportunity and proposes conclusions which are not warranted by the study methodology. We consider that raising vitamin D status in those with sub-optimal levels remains a valid means of protection against ARIs and COVID-19.