Effectiveness
Effectiveness means the extent to which a health activity's stated objectives have been met. The activity can be a specific intervention, procedure, regimen, or service. Effectiveness refers to how well a health activity works under real-world circumstances for a specified population, whereas efficacy refers to how well an intervention treats or prevents a health condition under ideal and controlled circumstances.
WHO Definition of Effectiveness
WHO Health Systems Strengthening Glossary [1]
Effectiveness: the extent to which a specific intervention, procedure, regimen or service, when deployed in the field in routine circumstances, does what it is intended to do for a specified population.
Other Definitions of Effectiveness
OECD [2]
Effectiveness means the extent to which the activity's stated objectives have been met.
Population Services International [3]
Effectiveness refers to how well an intervention works under real-world conditions, whereas efficacy refers to how well an intervention treats or prevents a condition under ideal and controlled conditions.
[1] WHO Health Systems Strengthening Glossary https://cdn.who.int/media/docs/default-source/documents/health-systems-strengthening-glossary.pdf
[2] Effects of European Union Accession, Part 1: Budgeting and Financial Control, OECD SIGMA Paper No. 19, March 1998, Appendix 3: List of Useful Terms
[3] PSI. 2007. Issue Brief Social Marketing and Communications for Health. Effectiveness of Male Condoms: Frequently Asked Questions.