In 2019 there were 4.66 million in the 50-54 age group.
As at March 21 60% of group 9 (50-54) had received their first vaccine. This was almost exclusively AZ (by March that was the predominant vaccine for first jabs)
So 60% of 4,666,000 is 2,799,600 of 50-54 years who have received their first jab of AZ. Am going to assume that half of those were women, hence it is likely that somewhere in the region of 1,399,800 50-54 year old UK women have had AZ by 21 March, and this figure will be growing as the vaccine programme continues to target that group.
Okay this is an educated guess not the actual hard data - but if there is a significant issue we should be seeing it soon