Herd Immunity Threshold Calculator
HIT from basic reproduction number (R0).
Medical Disclaimer
This calculator is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about your health. Never disregard professional medical advice or delay seeking it because of results from this tool.
Inputs
Results
Herd immunity threshold (%)
66.7%
How to Use This Calculator
- Enter Basic reproduction number (R0), Vaccine efficacy (%), and Population size.
- Review the Herd immunity threshold (%) (%) result.
- Use Required vaccination coverage (%) (%) and People to vaccinate to inform your decision.
How the result changes with Basic reproduction number (R0)
| Basic reproduction number (R0) | Herd immunity threshold (%) |
|---|---|
| 2.91 | 65.6% |
| 7.66 | 86.9% |
| 13 | 92.3% |
| 18 | 94.4% |
What each input means
- Basic reproduction number (R0)
- Average number of secondary infections from one case in a fully susceptible population.
- Vaccine efficacy (%)
- Vaccine efficacy in preventing transmission.
- Population size
- Total population size for absolute calculations.
What each result means
- Herd immunity threshold (%)
- Minimum proportion immune to stop sustained transmission.
- Required vaccination coverage (%)
- Vaccination rate needed accounting for vaccine efficacy.
- People to vaccinate
- Absolute number needing vaccination in the population.
- Effective R at target coverage
- Effective reproduction number when coverage target is met.
- Susceptible remaining
- Number of susceptible individuals remaining at HIT.
How this is calculated
Worked example, using the default values
- Identify Input ParametersBasic reproduction number (R0) = 3, Vaccine efficacy (%) = 90, Population size = 330000000 = 3 input(s) provided
- Calculate Herd immunity thresholdHerd immunity threshold66.7 = 66.7%
- Calculate Required vaccination coverageRequired vaccination coverage74.1 = 74.1%
- Calculate People to vaccinatePeople to vaccinate244530000 = 244530000
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