I've had good luck at avoiding a cold by taking vitamin D3 for several years at this point, keeping a testing level of around 50ng/ml. For that I have not felt a need for the flu shot. Don't believe the flu shot a bad idea. Do sometimes wonder how well it works from my observation of those that receive the shot. Seems many still come down with a cold over winter. But found what works well for me, and pleased about that.
I've read others reporting the same with D3.
"Unique vitamin D observations"
From the article:
...–Immunity from viral infections–I first learned of this association from Dr. John Cannell of the Vitamin D Council (www.vitamindcouncil.com). Dr. Cannell recounts his experience with the 2006 flu epidemic in the hospital in northern California, where he is a psychiatrist charged with the health of 200 inpatients held in closed wards. While the flu spread like wildfire to the patients in all the other wards, the 200 patients in Dr. Cannell’s ward failed to contract a single episode of flu while taking 2000 units of vitamin D per day.
I was a little skeptical at first, having been disappointed by the failure of several nutritional agents like zinc, vitamin C (perhaps, at best, a minimal effect). Now, three years into my vitamin D experience, I am absolutely convinced that Dr. Cannells’ early observation was correct: Vitamin D enhances immunity enormously. Not only have I personally not had a virus in several years, the majority of my staff and patients have been happily free of viral infections. There have been a few, to be sure. But the usual winters of hacking, coughing, and sneezing in the office have become largely a memory. It is a rare person who comes to the office with viral symptoms.