K. Shah et al.

The evidence regarding the efficacy of vitamin D supplementation in reducing severity of COVID-19 is still insufficient. This is partially due to the lack of primary robust trial-based data and heterogeneous study designs … This evidence summary, aims to study the effect of vitamin D supplementation on morbidity and mortality in hospitalized COVID-19 patients.

… The findings of this study show that vitamin D supplementation is effective in reducing the COVID-19 severity. Hence, vitamin D should be recommended as an adjuvant therapy for COVID-19.However, more robust and larger trials are required to substantiate it further.