It's also surprising that you've gotten 2 colds in the past few months when it sounds like you have been taking precautions due to covid-19. Seems like any exposure where you could catch a cold could easily have been Covid-19 instead, so you may want to re-evaluate your mask use, physical distancing, and hygiene practices.
I haven't had a cold since we initially locked-down in April, which is very unusual for me, but completely explained by social distancing.
Except you can, because that is the conclusion of at least one other study of the effect of Vitamin D. https://pubmed.ncbi.nlm.nih.gov/16959053/
Careful with Vitamin D. When you get a chance, go see your doctor and ask him to check your vitamin D levels. Don't forget to tell them you are taking suplements.
I swear, it's like people don't understand why we measure R_t. propagation is sigmoidal phenomenon. A reduction in transmission by 10% can easily lead to a reduction in prevalence by nearly 100%.
I used to get a major cold every 2-3 month and they were really bad lasting two weeks with fever, fatigue, coughs, colds, really stuffy nose, etc. Now? The two colds I've had were over in a week and the symptoms were so incredibly mild - mostly a light runny nose - that I'm legit grateful when I get a cold.
Regardless of vitamin D's effect on covid-19, the supplement has already paid off big time as far as I'm concerned. I've started to take 1g of vitamin C for the same reason, i.e. to boost my immune system. I should add that I live in a Nordic country with long dark winters and that I can't/don't go outside as much as I should.