To explore how the cost effectiveness of a behaviour-change prevention programme for sexually transmitted infection (STI) varies with the phase of an STI epidemic.
Earlier initiation of an intervention can improve the cost effectiveness of the intervention, although this result does not hold for all possible scenarios.
A model of STI transmission and standard methods of cost-effectiveness analysis was used to examine the cost effectiveness of a hypothetical, behaviour-change intervention initiated at various phases of an STI epidemic.
The intervention was more cost effective when initiated in earlier phases of the epidemic rather than later phases, under a range of scenarios. However, the relative impact of the timing of the initiation of the STI prevention intervention on the cost effectiveness was quite small compared with other important factors, such as the cost and impact of the intervention and the lifetime medical cost of the STI.