There was one whistle-blower from Pfizer who claimed that different batches had different concentrations of the various ingredients and that they were tracking the effects of the different formulations. Some were pure saline (as a control), while others had less of the active ingredients and some more, in several sets of percentages.
This seems likely given that one study released said that something like 80-90% of the short-term fatalities came from like one of 6-7 batches of the Pfizer jab.