The vaccine requires two doses to be fully effective. Additionally, the efficacy of the vaccine was only demonstrated with four weeks between doses (although perhaps new data suggests the 8-12 weeks the UK is putting between doses is effective - a brief literature search indicated people were calling for RCTs of this strategy around January but I'm not sure any data is available at this moment in time).
I think less than 1 percent of our population have had both jabs compared to some countries that are approaching 4 percent.
This isn't to say, just because it's not the roaring success we are lead to believe it is, doesn't mean it's at the other end of spectrum and should be deemed a failure.
Where did you get 1% from?
The logistics of vaccinating millions of people across the country, as more than 42 million people receive at least one dose.
Edit, I really should have read all the replies first.