It is defined as the average number of patients that must be vaccinated to prevent one case of disease.
It is a specific application of the number needed to treat metric (NNT).
For example, one study reported a number needed to vaccinate of 5206 for invasive pneumococcal disease.
[4] In order to determine a NNV, it is necessary to identify a specific population and a defined endpoint, because these can vary:[citation needed] Despite the limitations, the NNV can serve as a useful resource.
For example, it can be used to report the results of computer simulations of varying vaccination strategies.