[M T]

It seems you are assuming all the December doses will be first doses, and increasing production will account for second doses and the next round of first doses. 

I'm not sure that's how they are planning it, at least initially while production is still ramping up. I'm guessing they will not be putting shots in arms if they don't already have access to the second round shots for those patients. We already saw Pfizer had issues with production, would be a big problem if lots of people only got one dose and couldn't get the second from some snafu.

According to Gen. Perna, the Pfizer vaccine only has a 20 day shelf life (at least, that's how long after they deliver it) and requires 21 days between doses.  As the first distribution day will be on or after Dec. 11, no second doses to patients will be given in December.    (The Moderna vaccine has 28 days between doses and starts shipping Dec. 18 at the earliest.)

If problems develop with production in late December, then I can certainly imagine them hanging onto doses.  But I don't see stockpiling 50% and delivering the vaccine with only a couple of days left before it expires, hoping that everybody shows up for 2nd doses on time.

Gen. Perna did say something to the effect of having the second dose in hand when shipping the first dose, but I figured that had to be metaphorically because of the expiration.   Or maybe there is some way to have a dose such that its shelf life doesn't start until a final step.
But even if he was literal, he was still talking of 40M doses delivered in Dec, not 20M.

This does mean that for the Pfizer vaccine,  something like 2/3 of January's shipment will be 2nd doses for people.  For Moderna,  2nd doses will dominate the mid-Jan to mid-Feb shipments.

[M T]

It seems you are assuming all the December doses will be first doses, and increasing production will account for second doses and the next round of first doses. 

I'm not sure that's how they are planning it, at least initially while production is still ramping up. I'm guessing they will not be putting shots in arms if they don't already have access to the second round shots for those patients. We already saw Pfizer had issues with production, would be a big problem if lots of people only got one dose and couldn't get the second from some snafu.

According to Gen. Perna, the Pfizer vaccine only has a 20 day shelf life (at least, that's how long after they deliver it) and requires 21 days between doses.  As the first distribution day will be on or after Dec. 11, no second doses to patients will be given in December.    (The Moderna vaccine has 28 days between doses and starts shipping Dec. 18 at the earliest.)

If problems develop with production in late December, then I can certainly imagine them hanging onto doses.  But I don't see stockpiling 50% and delivering the vaccine with only a couple of days left before it expires, hoping that everybody shows up for 2nd doses on time.

Gen. Perna did say something to the effect of having the second dose in hand when shipping the first dose, but I figured that had to be metaphorically because of the expiration.   Or maybe there is some way to have a dose such that its shelf life doesn't start until a final step.
But even if he was literal, he was still talking of 40M doses delivered in Dec, not 20M.

This does mean that for the Pfizer vaccine,  something like 2/3 of January's shipment will be 2nd doses for people.  For Moderna,  2nd doses will dominate the mid-Jan to mid-Feb shipments.