The most recent news continues to reinforce the idea that AZ is simply not effective at ALL against the B.1.351 SA variant, which is worrisome if it ends up dominating outside of South Africa.
Pfizer and Moderna both seem to show lower neutralizing antibody responses, but not nothing, and while there is some question of if "2/3rds less is enough," there's also some other significant considerations around the T-cell response that's triggered by those two and its robust effectiveness even against B.1.351. But not so much with AZ, which continues to show itself as ineffective against the variant: https://www.medpagetoday.com/infectiousdisease/covid19/91658