It could do, but there are other known effects at work (such as temperature and humidity) that are known to contribute, and that would also be correlated with v

It could do, but there are other known effects at work (such as temperature and humidity) that are known to contribute, and that would also be correlated with vitamin D levels. You’d need to do a study to tease out the causality and the relative contribution of all those factors (if one hasn’t been done already). Edited to add: this looks like a reasonable review of the literature: https://www.annualreviews.org/doi/pdf/10.1146/annurev-virology-012420-022445 https://www.annualreviews.org/doi/pdf/10.1146/annurev-virolo...