I've been taking 5,000IU of vitamin D3 daily for years because the doctor thought it would be beneficial. I've been assured that that dosage isn't considered excessive. So what they're talking about in this article must be a much larger dose.
From Multiple Sclerosis News Today (March 2), "ACTRIMS2020:
Vitamin D at High Dose Can Worsen MS, Early Study Says":
#ACTRIMS2 2 - Vitamin D at High Dose Can Worsen MS, Study Reports