Mathematical modelling of effectiveness

Abstract

The effectiveness of a vaccine can be broadly defined as a practical measure of its costs and benefits when used in a community setting. What then is the relationship between a vaccine's efficacy and its effectiveness? Effectiveness certainly includes efficacy, but also encompasses secondary effects of vaccination, long-term efficacy of a vaccine (beyond that measured in conventional efficacy trials), the impact of vaccinating against one strain upon cross-reacting infections, costs of vaccination programmes and logistic considerations for vaccine delivery. This paper considers some of the biological determinants of effectiveness namely; secondary effects, long-term efficacy and competitive interactions amongst strains. Mathematical models of the transmission dynamics of infection and its disruption by vaccination are used as tools to help unravel some of the complexities that may arise when making interventions in non-linear biological systems.