The role of vitamin D as a preventive strategy in COVID-19 infections: evidence from South Asia

Background Regional evidence on prevention of COVID-19 and its sequalae by vitamin D remains inconclusive and sparse. Aim/Objective This study aimed to determine the association between COVID-19 and Vitamin D deficiency among adults in Colombo District, Sri Lanka. Methods A sex-matched case-control study was conducted among 104 RT-PCR-confirmed COVID-19 patients and 104 RT-PCR negative adults recruited from community. Non-fasting blood samples were analysed for serum 25(OH)D using chemiluminescence assay and vitamin D deficiency identified (< 50.0nmol/L). Results Cases (34.2; SD = 15.4nmol/L) had significantly lower 25(OH)D compared to controls (39.8; SD = 17.8nmol/L) (p = 0.02) which persisted after adjustments (p = 0.02), along with Sinhalese ethnicity (p < 0.001). VDD was significantly more prevalent in cases (83.7% vs. 71.2%; crude odds ratio (OR) = 2.1; 95%-CI:1.1,4.1), although not an independent COVID-19 predictor (adjusted OR = 1.9; 95%-CI:0.6,5.7). A significantly lower 25(OH)D level was observed in moderate/severe cases (39.7; SD = 12.3nmol/L) vs mild (32.9; SD = 15.8nmol/L) (p = 0.015). Neither low serum concentrations nor deficiency showed an independent relationship with severity (p > 0.05). Diabetes was the sole predictor of COVID-19 severity (p = 0.022). Conclusions Vitamin D has potential as a cost-effective primary, but not secondary, preventive strategy.