What's Scotland's vaccination roll-out doing? First doses have fallen off a cliff.

- It's not supply - they've heaps in their stockpiles & other nations with identical allocations are getting on
- It's not demand - there are plenty of Scottish 40-somethings ready to go. (1/)

I do have a suggestion of what's going on, but it's utterly speculative: I'd very much welcome alternative ideas / hypotheses / definitive statements from those in charge.

I suspect Scotland messed something up, fairly badly, about 11 weeks ago. (2/)

Here's the Scottish profile of first and second vaccinations by day. Look back 11 weeks to the first days of February, and you see a big, wide block of first doses being given - a total dose rate never matched since then.

They have to give all these people second doses soon. 3/

Let's guess for a moment that the 60k / day rate has not been hit again for a reason - that it is fairly close to the "front-end" flow capacity of the system.

That is, there are simply not enough vaccinators or vaccination centres to go much beyond that. (4/)

If that were true, then to squeeze the required second doses through your <60k/day "pipe" you'd need clear out first doses from the system and phase through that demand spike of second doses carefully.

In contrast to Scotland, look at somewhere like Wales:

Wales' total delivery capacity is clearly well within the first dose rates 11 weeks ago, and so they have plenty of room to continue first doses.

Similarly, England and NI appear fine for delivery capacity, and are also giving first doses (though cautiously) at the moment. (6/)

If this is so, then - like the other nations - Scotland has supply to continue 1st dose roll-out, but it is still forced to stop.

Avoiding this halt was very possible: by managing the first dose schedule, or by increasing capacity ... and they've had 11 weeks to get ready. (8/)

Of course there may be other reasons. We have data to show that Scotland's supply levels are fine (they publish dose deliveries, which far exceed doses issued) but if there's other - less incompetent - reasons why the first roll-out has stopped, I would love to know. (ends)