On the news today (watching Sky or I'd post link) and they is a Doctor saying that AZ doesn't work very well on the South African variant.
So with the news that AZ isn't being used on under 30's this less at risk group will be getting the more effective jab and those 30+ who are statistically more at risk of covid are going to be issued with a jab that not only risks clots but is less effective. Great.