It seems that the Oxford/AZ vaccine has two delivery vectors. One (two full doses two weeks apart) gave 62% protection the other (a half dose then a fill dose four weeks apart) gave 90% protection. 70.4% was the average since the 62% was the larger trial but I imagine the 90% is what will be given approval. How statistically significant it is I'm not sure.

Interestingly it seems no serious symptoms from either vector.