Because Vitamin C + D do not make you into superman.

Really, on your death bed, are you gonna start complaining to the universe: 'But, I took all the vitamins I could afford, I haven't had gluten in years, I'm not supposed to die.'

'What do you mean you wanna break up? Bitch don't you know I eat grass-fed liver twice a week? You don't deserve me.'

'Professor, I think I deserve an A on this test. I took all of the over-the-counter nootropics I could find!'

I also had a cold that lasted 1.5 weeks after Thanksgiving, and this is incredibly rare for me. I was also taking vitamin D3, and DayQuil to make it through a few work events, though I understand that it just suppresses the symptoms, but it barely did that. It was a weird cold, but it did come after being exposed to 5 different sick households, after a tour de New England and Long Island, plus having wheat products, so who knows what shot my immune system. The weirdest thing about it was that it was not really bad, just insistent and annoying. Maybe you had some naughty foods during the holidays?

The old folk saying still applies, "A cold is 3 days coming, 3 days with you and 3 days leaving." Except in my case the leaving part has always been more like 3 weeks of mild but annoying symptoms.

My theory is that it was just a cold that lasted a long while. I did all the "right" things and took all the supplements and bone broth too and I had it too. I just chalked it up to bad luck.

At the first sign of a virus, I take 40,000 IUs of Vitamin D3 for 2-3 days.

Haven't been sick at all in over 2 years.

It's important to get your D level tested and supplement to 50-80 ng/ml year-round. Magnesium supplementation is essential. A & K may be necessary, if you don't eat dairy or organ meats.