'diminish efficacy' is a correct and usable phrase in written English.
You can use it when referring to reducing the effectiveness or efficiency of something. For example: "The new regulations have been found to diminish the efficacy of the current system."
Although the CRAd expressing TK appeared to exhibit a slightly enhanced therapeutic efficacy both CRAds exhibited diminished efficacy when tumors contained in addition stromal cells.
Another factor that favors use of AAV5 for human gene therapy is the presence of AAV2 neutralizing antibodies in humans, which diminishes efficacy of AAV2 [42].
Preclinical studies almost invariably show diminishing efficacy with increasing pathology at initiation of treatment.
It has been theorized that incretin-based therapies have diminished efficacy with long-standing disease and fewer β-cells (15).
Importantly, SMN-restoring therapies demonstrate diminishing efficacy with delayed delivery consistent with the concept of a therapeutic window of opportunity for SMN-targeting therapies.
Person with HIV often find it difficult to maintain the adherence necessary for viral suppression due to many factors, including depressive symptoms; [ 10] even infrequent non-adherence greatly diminishes efficacy [ 2, 11, 12].
Although diazepam has been demonstrated not only superior to pill-placebo but also equally effective compared with alprazolam [ 56, 58], this issue could have diminished efficacy of diazepam and have diluted differences between combined therapy and psychotherapy alone.
Disadvantages of this procedure increase with time and include diminishing efficacy due to the unpredictability of subsequent individual hair loss, increasing cosmetic visibility of excision scars, potential gradual widening of scars due to stretching of adjacent scalp skin, and the usual need for more than one scalp reduction to effectively address hair loss (Unger and Unger 2003).
Not testing the partners might well diminish the efficacy of this simple field medicine approach.
