Like all vaccines it is mainly against severe symptoms.
And, as usual, all current data, still incomplete, suggest that all currently available vaccines are similar in efficacy. All the pfaffing about AZ being lesser than, badly made/designed/researched is simply distracting from the basic facts, it is a well known vaccine base and it works well. Like all the others!
We keep being told different things because no journalist likes to miss a bit of doom and gloom. Usually we wouldn't ever see any of the interim data, or be expected to work our way through all the varying opinions based on raw data, interim studoes and incomplete data sets.
Remember, all we are hearing now is about efficacy over and above "enough to save your life" The stuff that usually gets done over a decade or so of ongoing research! Again, the money being thrown at this is allowing the data to be crunched far more quickly than usual, so we see all the data as it is collated, in quick successsion. And again, journalists and SM commentators make much of any apparent contradictions. Some of them even know what they are doing when they spread disinformation based on this data, others, like most of the readers, don't understand enough to know what they are looking at.
The exciting bit is the new form of vaccine. When all of this is done and usted there is some amazng new medical research to be done on that!