{"knowledge_schema": {"broad_category": "Epidemiology \u2192 Vaccine Efficacy", "refinement": "This problem examines the relationship between incidence rates and vaccine efficacy in the context of an all-or-nothing vaccine scenario.", "specific_scope": "The focus is on understanding how the incidence rate ratio relates to the true vaccine efficacy when the vaccine provides complete protection or none at all.", "goal": "Determine whether the 1-incidence rate ratio will overestimate, underestimate, or correctly estimate the per-exposure vaccine efficacy."}, "summary": "In the context of an all-or-nothing vaccine, the 1-incidence rate ratio will underestimate the per-exposure vaccine efficacy. This is because the incidence rate ratio does not account for the complete protection provided by the vaccine, leading to a lower estimate of efficacy compared to the true effect of the vaccine."}