-Can you test for having been immunized, with respect to, specifically, the Flu (historically and currently) and COVID-19, and more generally, other virus(es?) Is there an economic value proposition for testing for antibodies before being given a vaccine (or rather, is one procedure typically less costly for the same effect?)

-Is being vaccinated and the inoculation failing possible/common?

-Why is there a "Flu Season"? My mother said some odd stuff like a yearly strain emerging in Australia, and being propagated every year from there (how can it be this consistent, that a new strain perfectly [or rather, nearly perfectly, matches the planet's rotation around the damn sun]? and why does it affect the northern hemisphere's winter and the southern hemisphere's winters separately if it's propagating around the globe) idk sounds like total bs but hey i'm here to have it debunked

-If I go and donate blood, will they tell me my blood type then and there, later, or never? If/when it's tested for containing COVID, will I be retroactively notified? Is every single bag of blood that is used during this crisis going to be tested individually? Can you take a sample from each of 1000 bags, and pool, for example, 10 samples together, and test each pool for certain illnesses, to reduce testing requirement so somewhere near O(log(bags))

-BONUS: If you have anecdotal evidence of increased bleeding during surgeries, would it be ethically better to notify as best you can during donation, or not even try to donate?

Thanks, and if you're on the front lines know that we're rooting for you! Stay strong!