Various studies are underway to identify protective variables for the COVID-19 pandemic. We hypothesized that if indeed the vitamin D levels would be protective in the European population, as recently proposed, the correlation would become more robust when the countries had passed the infection peak as on May 12 2020, compared to April 8 2020, when the majority had not. Comparative analysis of data from the mentioned stages indicated a significant increase in negative correlation of vitamin D levels with COVID-19 cases per million population in later stage (r(20): -0.5504; R2 = 0.3029; p value: 0.0119 vs r(20): -0.4435; R2 = 0.1967; p value: 0.0501), whereas the correlation with deaths per million population became insignificant (r(20): -0.3935; R2 = 0.1549; p value: 0.0860 vs r(20): -0.4378; R2 = 0.1917; p value: 0.0535). Considering divergence of vitamin D levels from the mean in subgroups, e.g. children, women, aged, dedicated exploratory studies with carefully chosen matched target groups is advisable.
Keywords: COVID-19; Correlation; Europe; SARS-CoV-2; Vitamin D.