That's one thing I like about Vitamin D: The high safe level is 100 ng/ml. Nobody is ever harmed by keeping their blood levels below that number. Doctors routinely treat Vitamin D deficiency with single injections of 90,000 iu followed by high D3 supplementation. There has been some concern in the past about Vitamin D overdose causing calcium deposits, but it's extremely rare to see that at blood levels below 100 ng/ml. One case had a patient taking some huge overdose because of a label mixup, and he had no overdose symptoms.

There have been hundreds of peer-reviewed journal papers showing Vitamin D participation in all sorts of immune and other bodily functions. I have never seen one on the back-edge of the Vitamin D sword. So taking a safe amount of Vitamin D3 is extremely unlikely to harm anyone. It's also extremely cheap.

Ask you doctor, or look up your blood level in your medical records if you had it tested. Your doctor can tell you about the recent clinical info that supports regular Vitamin D supplementation. The optimal value seems to be 30 ng/ml. Most Americans are below that, and some are far below that.

That Indonesia paper was far from the first on the topic. In regards to Covid-19, doctors have reported that their ICU patients (including young people) are almost uniformly deficient in Vitamin D.