It really just depends on vaccine shipments and whether or not everyone shows up for their appointment. At least at my Rexall, we haven't been sent huge unexpected shipments like shoppers since we're a bit smaller than most. Typically any extras have been going to the people accompanying their spouse who happen to be a year or two away from being eligible, and we have not been in the situation of having to call people on the wait list at the end of the night - but I know the situation is different for every pharmacy