Anecdotal story:

I was told pre-COVID I had to take Vitamin D daily, even after being outside an hour+ daily (also, took 0 other medicine outside of vitamins.) I’m grateful for that since I believe I had COVID in January 2020. At the time, others around me were diagnosed with “bacterial sinus infections” that spread like wild fire and forced people out for about a week. As with any job, I eventually did get it but it lasted only 2 days with muscle aches and a fever. I’ve had sinus infections before but not one that lasted 2 days with no medication! Only thing it could have been was the Kung Flu and I believe Vitamin D easily helped keep it down.