All my kidding aside, I’m convinced (as you seem to be) that nutrition and hygiene are far more effective than vaccine, especially for flu. That’s a general statement, and I believe there are exceptions.
I have had maybe one flu shot in my 50+ years, and don’t plan another one any time soon.
The Vitamin D supplementation is interesting for a lot of reasons. One is that a friend of mine who suffers from Rheumatoid Arthritis has been taking prescription massive strength Vitamin D. It's truly helped ease her pain.
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