COVID-19: Every UK adult could be offered a vaccine by mid-July - if these figures are anything to go by

For a few hours this week, we were given an insight into the closely-guarded secret at the centre of the UK's vaccination programme.

It came courtesy of the Scottish government, which published its vaccination plan on Wednesday.

The plan included detailed figures for the number of vaccines that would be supplied to Scotland by the UK each week until the end of May.

The UK government objected, saying the publication of the figures would create difficulties for the pharmaceutical companies, and the offending page was quickly removed - but not before some clever internet users were able to save a copy.

This is what those numbers showed:

The reason this information is so valuable is because it allows us to get a sense of perhaps the most crucial piece of data in the entire vaccination programme: the number of vaccines available to the governments of the UK.

The UK government has promised to offer COVID-19 vaccines to 15 million vulnerable people by the middle of February.

More than a month into the programme, it's managed to give 3.2 million people a jab. By international standards this is impressive. What's more, according to today's figures, the daily rate is now close to what is needed for the government to hit its goal.

Ministers have said that the limiting factor is supply of the vaccine, but the government has not published any figures on exactly how many vaccines the UK is expecting.

Without these numbers it's very hard to judge the UK's progress. We only have the assurances from ministers - which, for understandable reasons, many people are reluctant to rely on.

The Scottish government figures give us a real sense of what is possible. As the chart below shows, with this supply of vaccines, Scotland could give every person in the priority groups a first dose by the middle of March.

That includes everyone over 50 and everyone over 16 with serious underlying health conditions.

Assuming that there are no problems with the supply or the delivery, Scotland will have enough vaccine to offer two doses to every adult in the country by the middle of July.

In practice, not everyone will take up the offer of a vaccine so these targets could be reached even faster. The Scottish government itself is expecting 80% take-up; our numbers are based on 100% take-up.

We can also use these numbers to estimate when the UK as a whole will get its vaccines. This involves making some assumptions, so any figures should be taken with a pinch of salt.

But the results these numbers produce explains why, behind the scenes, ministers are so confident about the rollout of the vaccine.

If Scotland has been given a supply of vaccine proportional to its per capita share of the UK's population, as sources with experience of UK-wide immunisation programmes say is normal, then the UK will easily have enough vaccine to make its February target.

It, too, will be able to offer every single adult in the UK a dose by mid-July.

Of course there are many things that could go wrong from here. Raw materials can run short. Vaccines can get lost or wasted.

But there are reasons to be optimistic.

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The Scottish government says that its numbers are based on the worst-case scenario provided by the Westminster government.

The Scottish government has also allowed for 5% wastage, even though in reality it says the real amount of wastage is 1%.

It may seem hard to believe, but based on these figures, and the increasingly positive noises coming out of Westminster, the UK government vaccination programme is on track to under-promise and over-deliver.