It shows a linear correlation, or maybe forced into one by linear regression, that shows that the vitamin does seem to have a beneficial effect in suppressing the number of cases. (The graph itself is credited to the University of East Anglia-maybe someone got their wires crossed.) The variance is pretty big but it is a generally linear correlation. Countries like Sweden and Slovakia with very high levels of vitamin D in their system do have relatively few cases of the disease. In the case of Sweden , it is surmised that although the sunlight is less intense, Swedes are an outdoor people and get in the sun as much as possible. On the other hand, in Spain which has a lot of sun, the inhabitants have the tradition of covering themselves up against it.
Interestingly, the UK although having less vitamin than other countries falls well below the regression line for the number of cases. Ther does seem to me to be a conrsdiction here because ootherwise the course of the disease follows vert closely Italy, France and Spain. The real outlier though, is Iceland, which would appear to have nearly 4 times the number of cases than their vitamin level would predict. Very weird.
An interesting point that does come out of this rather loose correlation is that it may account for the abnormal sensitivity of black and ethnic minorities to the disease. Genetically, they are primed to make enough vitamin D in very strong sunshine. When they come to our cooler latitudes, they can no longer generate enough vitamin D for health. I have not yet seen this point discussed but it is an interesting theory.