Many countries have Vitamin D deficient populations, including Italy: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5986426/

In Italy, it gets worse the older the population gets.

It is also an issue in Germany: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4499202/

I make no claims other than: 1) there is a very strong correlation between vitamin D insufficiency/deficiency and poor outcomes for COVID-19, and 2) many populations, including those in sunny countries, suffer from widespread vitamin D insufficiency.

I for one have been taking 1,000 IUs of vitamin D every day since March, and trying to get sun exposure mid-day whenever I can.