Get some liposomal C. Save it in the fridge for when you feel a bug coming on, and take 1-2 tsp a day until you feel well. Or ask Jane along how to make it. One day maybe I will cause it is expensive. But it works. Zinc works well too. Best tasting zinc lozenges come In a little roll and are elderberry flavored. But there are the cheaper more commercial ones - again, these are to take - sucking or gently chewing them in the mouth - 3 X a day when you feel a bit sick. Or really sick. They cut colds short.
Vitamin d needs to be taken every day without fail unless a lot of your body was in the sunshine that day. Then you can skip. And most adults will need 5k to 10k or more a day to get their blood levels up to over 60, over 80 if they have any chronic conditions, over 90 if cancer lurks.
If you take Vit D supplements, you may want to research the Vit D and Vit K2 connection. Very important!
The elderberry flavored zinc sounds good, though. I'll get some.
Take 5000 units a day. Had a severe shortage when I worked in a room without windows for thirty years.
Prayers for me and Mrs Trump. That they stay safe and have a glorious victory today.