I was involved in getting the #oxfordvaccine @JennerInstitute manufacturing process and consortium up and running. Here is a thread of why there is an issue with doses, with some science and #sciencepolicy. The EU looks in the wrong to me.

To make the vaccine, you need to grow up a huge volume of cells, they make the vaccine, then the vaccine is purified. The manufacturing process is new. It relies on elements used before, but each new process has its own parameters.

That means each manufacturing site has to on board the exact process and get it running. Usually this takes many months, but is being done urgently for COVID.

When you book manufacturing capacity, you are booking the manufacturing slot. It might take 2 weeks to make a batch of vaccine. With a new process, you always get the same vaccine, but the yield can vary.

Maybe a good yield is a million doses per run (in reality, it depends on how big your cell culture is). But maybe the first few runs only yield 250 thousand doses.