A synthesis of economic data from randomized trials of recipient-focused interventions to increase vaccine uptake

Introduction
Achieving high vaccine uptake is key to maximizing the effectiveness of immunization programmes. Decisions around which interventions to implement to increase vaccine uptake need to be informed by both intervention effectiveness and the economic data. We aimed to collate cost analyses and economic evaluations of recipient-focused interventions to increase vaccine uptake for high and upper-middle income countries.

Methods
We conducted a review of the economic evidence, alongside a systematic review of randomized controlled trials (RCTs) on the effectiveness of interventions to increase vaccine uptake. Eligible studies were those reporting economic data (including economic evaluations or cost analyses) pertaining to RCTs included in the systematic review. These studies were identified in two ways: firstly, through the comprehensive systematic review searches (up to April 2024), and secondly, through a targeted search for economic information conducted on MEDLINE to March 2024 and the archived NHS Economic Evaluation Database (EED). The quality of economic evaluations was assessed using the Drummond checklist. Data were narratively synthesized.

Results
We screened 2803 reports in total, of which 37 studies met our eligibility criteria. Sixteen conducted full economic evaluations and ten conducted cost analyses, while the remaining ten reported the value of financial incentives that contribute to intervention costs. All cost analyses estimated direct costs related to the implementation of interventions, with substantial variation in terms of cost components. Economic data were most commonly reported for interventions to increase uptake of influenza (n = 15) and human papillomavirus (n = 11) vaccines. Of the included studies, most related to reminder interventions (n = 13).

Conclusion
Our review highlights a lack of both cost data and full economic evaluations for trials of interventions to increase vaccine uptake. Collecting and reporting relevant economic data in a consistent way is vital for enabling informed decision-making around which interventions to implement.