Vaccine efficacy vs effectiveness

Efficacy is performance under ideal and controlled circumstances, whereas effectiveness refers to performance under ‘real-world’ conditions. Read more about this here:

• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3798059/
• https://www.who.int/influenza_vaccines_plan/resources/Session4_VEfficacy_VEffectiveness.PDF
• https://www.immune.org.nz/vaccines/efficiency-effectiveness
• https://www.cdc.gov/flu/vaccines-work/effectivenessqa.htm