A quick comparison with per country pop mortality rate charts would quickly dispel any correlation with vit. D whatsoever:
https://boogheta.github.io/coronavirus-countries/#deceased&log&ratio&align=10th%20case&alignTo=deceased
https://www.worldometers.info/coronavirus/
https://91-divoc.com/pages/covid-visualization/?chart=countries-normalized&highlight=(None)&show=all&trendline=default&y=fixed&scale=log&data=deaths#countries-normalized
https://covid19info.live/