I think it's all from the same study though, where 3000 Health care workers in Delhi were given the AZ jab and only 3% later became infected during the study. That doesn't mean the vaccine was 97% effective against the Indian strain though and shouldn't be taken that way, as surely there's no way of knowing how many of those workers were exposed to it in that time? I don't argue it will have prevented some transmission but how much is difficult to prove. I just don't understand how that 3% figure can be reversed to reveal 97% efficacy when it doesn't necessarily mean anything like that.
Apologies if this is a different study or my interpretation is incorrect, this is just my understanding of it.