[lambdaba]

Haven't people changed their behavior though? Avoiding going outside, having fewer diversity in social interactions but longer durations, and indoors.

There is definitely evidence for vitamin D, it's odd this is still not yet widely acknowledged, I can't say I reviewed the research myself but credible people have and have been spreading the information. I've definitely heard of some governments having taken measures for prevention with vitamin D, but there are also some results if administered early enough after infection.

Vitamin D is essential for immune system function, but the wider picture is more complex with high vitamin D levels also correlating with better nutrition (diets higher in cholesterol, which is essential for hormone synthesis - is generally lower in people having severe forms), better immune system function (infections deplete vitamin D), and even activity levels (spending more time outside).

[stefan_]

There are working vaccines but we still have Vitamin D clowns on HN. Can we just ban this already?

[detaro]

"There are working vaccines" isn't particularly immediately useful for the billions of us that don't have them yet, so it's not surprising people find preventative things relevant. (+ the Vitamin D thing has at least the fact going for it that even if it doesn't do anything it's still a sensible overall health consideration)