Vaccines · Pharmacology

In vaccine clinical trials, what is the key difference between measuring vaccine 'efficacy' versus measuring vaccine 'effectiveness'?

  1. Efficacy is measured in animal models; effectiveness, in cell cultures.
  2. Efficacy is performance under ideal trial conditions; effectiveness, in the real world.
  3. Efficacy focuses only on safety; effectiveness, only on antibody counts.
  4. There is no difference; the words are used interchangeably in publications.
Show answer and explanation

Correct answer: Efficacy is performance under ideal trial conditions; effectiveness, in the real world.

Vaccine efficacy is calculated from randomized controlled trials where conditions are strictly managed, and participants are highly select. Vaccine effectiveness measures how well the vaccine protects the general, messy population in real-world field conditions, accounting for variables like improper cold chain storage, missed doses, and diverse underlying health profiles.

Difficulty: Medium Question 23 of 25

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