Vitamin D plays a big role in immune function, and is linked to spinal surgery recovery. Searching for 'vitamin d spinal fusion recovery' gets quite a few hits, and if you have an hour to kill, is an overkill lecture that explains some of the effects on immune function.
FWLIW, I think a daily dose of ~1,000 IU D3 per day for ever 25 pounds of body weight is a reasonable place to start. I started taking coincidentally this much at the beginning of 2020 because I didn't want to die from the bug. Surprisingly, it did wonderful things for my OA hip, a long-ago-injured ankle, and my aching back. Forget food sources - that dairy serving has maybe 50iu in it. Unless you eat salmon and seal blubber every day, you really can't get enough in your diet. And casual sun exposure in NYC isn't going to do a hell of a lot either. (People are 'supposed' to be running around in the sun, making thousands of IU every day.) VD increases your intestines' ability to extract calcium from your food, so there is probably no need for CA supplements when taking largish doses of D3.
Good luck!