Hi ScenicViewer - yes Bioflavonoids - sorry I didn't get the name right. I am in UK and I bought Vit C-1000mg with Rose Hips from Holland & Barratt.
The lady told me to take double the daily dose which I did while I was so ill with a death rattle, endless dry cough. Where I worked, I was right next to a public health team who were surprised but curious at what I had been told. Taking double the daily dose is not recommended but I was told it so firmly and I was so ill, I did and I made a full recovery.
I did not have Corona virus, it was long before that. I had been pioneering and the routine was stressful and I could not rest properly. So the cough probably had more to do with acid reflux rather than an infection. But her advice was the only thing that provided me with any relief.