Authors may calculate a (vaccine efficacy level) of some percent.
A (vaccine efficacy level) can be constituted-of-or-filled-with some percent.
A size of an (efficacy trial) may depend upon an incidence of disease.
(Treatment research) may be focussed on studying an efficacy of (treatment interventions).
A trial may compare an efficacy of transplantation with transplantation.
A springboard can be for testing an efficacy of some (prevention program).