If the supply of Hosts at Mass runs low, of course the priest or Eucharistic minister may break Hosts in half (or quarters, etc) to satisfy demand. And that’s fine - Jesus is fully present in the smallest piece. Nobody gets “more Jesus” or “less Jesus.”
But that system really works well if there is only the priest distributing, as he can gauge both the supply and the demand, and he can sense when it is necessary to start breaking Hosts.
But with multiple people distributing the Host it gets more complicated, because nobody really knows how many Hosts are available in total. I have observed instances where one minister “runs out” and withdraws, allowing other ministers to fill the void. The first minister simply assumes that other ministers are able to meet the need (and, so far, this has worked, in my observation), and no Hosts are ever broken.
But what happens if everyone runs out at the same time? (assuming there are no reserve Hosts in the Tabernacle)
For sake of discussion, we will assume that the Precious Blood has also been depleted (which I have observed numerous times). And we’ll assume nobody has taken a Host in a pyx to deliver to a homebound person.