I believe they use the one-shot AstraZeneca vaccine in the UK as well as what we use.
Most people in the US get the two-dose mRNA vaccines, which I believe are more effective.
Break it down by vaccine manufacturer and co-existing conditions.
AstraZeneca is two-shot, but with a standard 12-week delay between 1 and 2. Its not always delayed that long in practice outside the UK.