>I don't know how you can dispute that if you are trying to compute A where A = B/C and you don't have a fixed value for B, then you cannot know A with any certainty.

I'll argue that C, the benefits, are also unknown. What about the long term effects of COVID-19? What if a new more deadly, more infectious or vaccine-resistant variant appears that could have been prevented from a quick mass vaccination?

You can only make the best decision from what we know at this time.