Enteric fever remains a major global health challenge, mainly affecting children in settings with poor sanitation and limited access to safe water. In response, over 60 million doses of typhoid conjugate vaccine (TCV) have been introduced in the past three years. However, follow-up data from trials in Malawi and Bangladesh indicate variability in the duration of vaccine-derived protection, raising important questions about the role of the force of infection (FOI) in affecting vaccine effectiveness over time. Understanding how FOI influences the waning of protection is critical, as it directly affects estimates of long-term TCV impact and cost-effectiveness, which are key parameters for policy decisions on vaccine schedules. In this modelling study, we will investigate the relationship between FOI and the duration of protection following a single dose of Vi-TT, using existing individual-level immunogenicity and efficacy data. We will then update our previous modelling analyses to assess the long-term impact and cost-effectiveness of TCV strategies, with and without booster doses, tailored to settings with varying typhoid burdens. The findings will generate essential evidence to inform WHO and national policy decisions on TCV booster recommendations and help determine whether a single-dose strategy is sufficient for sustained typhoid control in diverse contexts.