In epidemiology, the relative risk reduction (RRR) or efficacy is the relative decrease in the risk is the incidence in the unexposed group. If the risk of an adverse event is increased by the exposure rather than decreased, the term relative risk increase. If the direction of risk change is not assumed, the term relative effect is used, and it is computed in the same way as relative risk increase.

Numerical examples

Risk reduction

Risk increase

See also

• Population Impact Measures

• Vaccine efficacy

References