No, "affective vulnerability" is a term, it's not "effective" (well, maybe that's what wotcher's T meant, what do I know )

There are different kinds of vulnerability. Biological vulnerability, such as allergies for instance, or if a person is prone to certain physical illnesses. Cognitive vulnerability, which is to do with patterns of thinking or faulty beliefs that make us more vulnerable to mental illnesses; I believe pathological paranoia could be a kind of cognitive vulnerability, for instance.

I think "affective vulnerability" basically means "emotional vulnerability", that is to say, having to do with feelings (or affects, which are not quite the same thing - littleplum's definition is spot on) being maladaptive. It's generally considered to be a good thing to be able to be vulnerable in the right context, but that doesn't mean that all vulnerability is always positive, and sometimes it can hinder our mental wellbeing very much.

An example of the above: I react with the affect shame in many situations where it's not really appropriate. That makes me vulnerable to, for instance, receiving certain kinds of praise. And that's not a positive form of vulnerability.