Vaccine efficacy
Gist
It describes the proportional reduction in infection among the vaccinated group compared to the unvaccinated group (placebo). Note that in a non-clinical setting, it's called vaccine effectiveness.
Here's an example of what it looks like in a paper:
Formula
- If ARU and ARV are Attack Rates of the unvaccinated and vaccinated group respectively. Then Vaccine efficacy (VE) can be calculated as:
- Alternatively, one can use Risk ratio:
Interpretation
If the attack rate of the vaccinated group is higher, then VE can be negative!