I didn’t think that was the case. I thought that the vials held the same volume regardless. But each vial has some “extra” to account for lost volume in extraction. Let’s say it had 5% extra per dose. That’s almost enough for a complete 6th dose, but not quite. But, if you use a more efficient syringe, then you might save an additional 1% per dose. So now, your 5 dose vial has enough “extra” volume for a complete 6th dose. And the manufacturing doesn’t need to change.

That’s the benefit.

Note: this was always accounted for as “extra” doses. It was part of the plan that there would be extra volume for each vial that could be pooled together for extra full doses. But because they are “extra”, you couldn’t plan on there always being that extra dose (or over the course of a day how many extra doses).

You do need a specific type of syringe in order to extract the 6th dose correctly and it was not the case that 100% of the distribution was set up with that particular syringe in mind.

Yes. You need vaccines and needles with low dead space. They could comfortably extract 6 and even in some cases 7 doses from vials.

Initially some doses were wasted because it was unclear whether that was a legitimate thing to do.

Then, after explicit guidance, they said "OK, these count as 6 doses, then, for the purpose of our Federal contract!"

Then, Feds scrambled to ship supplies to ensure low-dead-space syringes were being used everywhere.

Nah. That's a good rule. Pooling of vials has caused contamination and severe consequences to patients in the past, and it also compromises traceability.

Having bad outcomes from pooling and not knowing whether it came from the combining practice, a certain vial, an entire lot, or even worse-- the fundamental vaccine-- could take the entire vaccination program off the rails. That's not worth it to stretch supplies a few percent.

Just to make sure it's clear to everyone, you need to extract every dose with the special syringes - not just the 6th one. If you use the low dead space syringes for the first 5 doses, the efficiencies add up to enough solution left over for a guaranteed 6th one.

But you can’t count that retroactively for vials where 5 shots were administered and at that point the vial was empty. You can only count that for unopened vials.

Right, but this is a dispute over something they didn't do.

You can count 6 shots if 6 shots were given. That's what's happening.

Correct, but nobody tried to do that.