[pitpatagain]

I think it's pretty clear that being easier to take and not mess up is the reason for the difference in statistical effectiveness. The reason for lower numbers for effectiveness of daily oral Truvada prep is primarily measuring differences in adherence.

[Fomite]

We actually have terms for this.

"Efficacy" is how well something works under ideal conditions.

"Effectiveness" is how well something works in the real world.

So yes - "This is more effective because adherence is easier" is both true and intended.

[Ericson2314]

Just so where clear, from a public health as opposed to basic science standpoint, that's a distinction without a difference.

people magically get more vigilant is as leakly as virus magically goes away on its own.

[pitpatagain]

Yes, my phrasing was responding to the way the parent stated it as "90% more effective, and also it's easier to take". As you say: It's 90% more effective precisely because it's easier, not and also. Behavioral factors matter an enormous amount for the real world success of many types of drugs!