AZ at present has a 63% efficacy rating ...
What is your source for that please?
https://www.who.int/news-room/featur...u-need-to-know
That's the WHO rundown on it, under how effective it towards the bottom;
The AZD1222 vaccine against COVID-19 has an efficacy of 63.09% against symptomatic SARS-CoV-2 infection.
It does say longer dose intervals increase that but does not specify by how much.