####
Press the
**Calculate**
button in the lower left corner to perform the sample size calculations

### Introduction

This web application performs sample size calculations for cohort and test negative design studies on brand-specific vaccine effectiveness (VE), and relative VE of one vaccine over another. The sample size calculations are adjusted for confounders, and subject dropout. For sample sizes in test negative design studies, this application also provides the size of the catchment that is required to obtain the required sample size.

### Definition of vaccine effectiveness (VE)

#### Cohort study (incidence risk ratio)

We define absolute VE of a vaccine as
*1 - Relative risk of being a case in vaccinated subjects over unvaccinated subjects*
. Similarly, we define relative VE as
*1 - Relative risk of being a case in subjects vaccinated with one vaccine over another vaccine*
.

#### Cohort study (incidence rate ratio)

We define absolute VE of a vaccine as
*1 - Ratio of incidence rate of being a case in vaccinated subjects over unvaccinated subjects*
. Similarly, we define relative VE as
*1 - Ratio of incidence rate of being a case in subjects vaccinated with one vaccine over another vaccine*
.

#### Test negative design studies (odds ratio)

We define absolute VE of a vaccine as
*1 - odds of being vaccinated among cases divided by the odds of being vaccinated among control subjects*
. Similarly, we define relative VE as
*1 - odds of being vaccinated with a particular vaccine versus the reference vaccine among cases divided by odds being vaccinated with a particular vaccine versus the reference vaccine among controls*
.

### Questions or Suggestions?

Please contact: anirudh.tomer@p-95.com