People are getting confused:
The Biden administration's base goal is 100M doses (jabs in arms) in 100 days. When that was announced, the rate of jabbing was shockingly low such that it seemed likely that that goal wasn't going to be achieved. So, the Biden administration set a baseline goal to ramp up jabbing.
When you talk about the number of people fully immunized, that's 50M because it takes two jabs.
When you talk about "this Summer" or "June" you're talking about the totality of all jabs to get us to herd immunity, not what's happening short term in the next 100 days.
Pfizer and Moderna should be providing more than 100M doses in 100 days, but the question is, can we get those doses into people, or will states continue to be a mess in their delivery system? The current administration's goal is to help states jab people at the rate that doses are produced... for now, over the next 3 months.
By the end of 3 months, other company's doses should be in the system, and the system should be able to handle the increased jab-load.
The states, scrambling on their own, have just started to reach 1M jabs/day, making 100M jabs in 100 days likely.