Vaccine Effectiveness or Efficacy From Attack Rates
Vaccine efficacy or effectiveness from the attack rates among vaccinated and unvaccinated people: 1 minus the risk ratio, with its 95% interval.
Open the tool → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Efficacy (trial) or effectiveness
- Effectiveness (field conditions)
- Cases among the vaccinated
- 18
- Vaccinated persons
- 152
- Cases among the unvaccinated
- 3
- Unvaccinated persons
- 7
Result: Vaccine effectiveness 72.4%: 1 − risk ratio 0.28.
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What you enter
- Efficacy (trial) or effectiveness (field)
- Cases among the vaccinated
- Vaccinated persons
- Cases among the unvaccinated
- Unvaccinated persons
How this is calculated
Citation
CDC. Principles of Epidemiology in Public Health Practice, 3rd ed., Lesson 3, section 6: vaccine efficacy or effectiveness, with the varicella example of Table 3.13. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.