AstraZeneca has no experience developing vaccines. As a result they’ve massively screwed up multiple times before. Frankly, even the original approval they got from the UK should never have been given, considering how tainted their original trials in Brazil were.

Basically what seems to have happened is that Oxford university developed the vaccine, required that companies who wanted to manufacture and sell it should not make a profit, and therefore only got companies with little vaccine development experience, such as AstraZeneca, which probably due to their lack of experience has been making mistake after mistake.

That being said, we have seen that with COVID the vast majority of vaccines have been extremely successful (some like the Russian and Chinese ones were deployed without complete testing and were shown to have great results), and since we are confident the AZ vaccine is safe enough, ans we can see the impact in the UK, there’s a strong justification to authorize using it even without proper results.

Just not in the US, which already has access to enough vaccines for its population without needing the AZ zone.