If Vitamin D had such a major effect, I would have expected death rates from Southern Europe (Spain, Italy specifically) to be a lot lower than from Northern Eu

If Vitamin D had such a major effect, I would have expected death rates from Southern Europe (Spain, Italy specifically) to be a lot lower than from Northern Europe (e.g. UK, Germany). From my anecdotal experience people in Southern Europe spend a lot more time outside (in parts of Spain you can still go to the beach now, where I live there is snow on the ground...), and older people seem more active and able to live independent lives (i.e. not in a care home). Of course this doesn't mean Vitamin D isn't at play. The one thing this pandemic has taught me is it seems there is very little we know about how it works :-) Maybe production from sun exposure in older people drops greatly, so the difference in sun exposure has little effect on overall Vitamin D levels.