The analogy to our study I can think of is the allergy treatment study. Say, you have a procedure that can alleviate or eliminate the allergy produced by a laboratory setup, in which the subject is given a certain mount of allergic agent in a certain period of time of exposure. Two groups of subjects, active treatment and control are used in the study. Before the treatment, they all respond to the agency with different severity. After the treatment, there are 50% of active group who are immune to the agent and the other 50% has reduced severity. The control group are all responded the same as before.

This is one time treatment. After one year, only 20% of active group are impervious to the agent and the other 80% are still have reduced severity. THe control group has no change.

I am thinking about the clinical significance. The occurrence of allergy before the treatment in active group is 100% and immediately after the treatment is educed to 50% , in one year it is to 80%. Is this significant clinically? However, if you look at the reduction in severity, it might have >50% subjects in active group who's symptoms are reduced by 50% in a year.

I don't know in this case it is preventive or treatment. Looks like both are applicable.