In a phase III randomized controlled trial, a new dengue vaccine shows 80% efficacy in preventing virologically confirmed dengue. When the same vaccine is rolled out in a national immunization program, the observed reduction in dengue hospitalizations is only 65%. This difference between trial results and real-world outcome is best described as the distinction between:

• A Herd immunity and individual protection
• B Immunogenicity and reactogenicity
• C Protective titre and seroconversion rate
• D Efficacy and effectiveness ✓

Explanation

Efficacy is measured under ideal, controlled conditions in randomized trials with strict inclusion criteria. Effectiveness reflects real-world performance in diverse populations with variable cold chain, co-morbidities, and compliance. Effectiveness is almost always lower than efficacy. This distinction is fundamental in vaccinology and frequently examined.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.