It boils down to either:

1. bad quality control (not likely)
2. cheating by the pharma cos to make batches cheaper and not catchable that they did that. $710 per vial pure profit, by the price they bill the gov't.
3. decision to taper down the death rate by randomly giving saline, so as not to be instantly obvious (a plausible strategy).
4. some infiltration of the medical system perhaps, but would be noticeable if nurses were directed to different vials for different patients.

The problem is, all four alternatives are unacceptable. This leads to the most likely is the one that benefits the elite the most. I vote for #3. Because #2 would be expensive if they got caught doing it.