So here is my best explanation as to the gap between Ottawa saying Pfizer will deliver 4-million doses and some provinces saying it will only be 3.5 million doses. (a short thread)

Pfizer has sent a new shipment schedule based on a new assumption that you can get 6 doses per vial. Canada has been operating under the assumption that there are only 5 doses per vial. The 6 dose standard has been approved in Europe. It is under review in Canada.

Pfizer clearly anticipates Canada adopting that same standard. So the delivery schedule shared with provinces today reflects that. It means fewer vials. But still 4-million doses if you get 6 doses per vial.

But if Canada does NOT approve the 6 dose standard Pfizer has agreed to send enough vials to provide 4-million doses based on 5 doses per vial. This is what it agreed to when it signed its contracts with Canada.

So its easy to see how this causes alarm and confusion. The key is to draw a distinction between number of vials and number of doses, the latter changes based on this 6 vs 5 dose decision.

It means the shipment numbers will be adjusted upwards if the 5 dose standard prevails. It will likely stay the same if 6 doses are adopted.

TL:DR
Scenario 1. Pfizer gets the approval of six doses per vial. Vial numbers the data shared today stays the same

Scenario 2. Pfizer doesn't get approval. They'll send more vial to meet the 4m in the contract

The problem here is that the new delivery numbers got leaked without any of the context. And the explanations of that context have been less than clear.