I do not recall any “research” as of yet that “proves” this. Medical research is still at the point of trying to prove that low Vitamin D levels cause disease and not that disease comes first which then causes low Vitamin D levels.
Having said this back in 2009 Dr. Cannell said “Stock your home’s pharmacy with several fresh bottles of 50,000 IU capsules of Vitamin D3 (at this dosage it is a medicine, not a supplement) and if you get this flu (see below), take 2,000 IU per kg of body weight per day for a week.” “As I weigh 220 pounds, I would take 200,000 IU per day for seven days if I thought I had an infection with a 1918-like influenza virus.”
It only “makes sense” to me that illness or injury would increase the need for more Vitamin D at least in the short run maybe even the long run. This is why we usually suggest that someone with a disease keep their levels higher than 50ng/ml. I have also suggested to people that if they are “stressed” meaning the emotional type, that they might want to increase the amount they take. I actually had someone once who said “I was doing so much better but there has been some family stress lately and now I have regressed somewhat.”
So you said illness and injury and I am going to add mental stress, surgery and pregnancy.