Incentives in immunisation campaigns in low- and middle-income countries: a scoping review mapping evidence on effectiveness and unintended consequences.

introductionVarious incentive programmes are being used to improve immunisation uptake, despite limited understanding of their effectiveness and potential unintended consequences. We conducted a scoping review to map and synthesise evidence on their use in low- and middle-income countries (LMIC), compare experiences across regions and incentive types, and identify unintended consequences and implementation challenges.

methodsWe searched Ovid MEDLINE and grey literature for studies published between 2000 and 2024 investigating incentives in immunisation campaigns in LMIC. We included quantitative and qualitative studies investigating monetary or non-monetary incentives provided conditionally or unconditionally on immunisation uptake. Data were synthesised narratively to summarise evidence on effectiveness, perceptions and attitudes and unintended consequences.

resultsWe included 40 studies from 19 countries (20 from Africa, 13 from Asia and seven from Latin America). Of these, 31 evaluated effectiveness through randomised trials (n=17) or quasi-experimental designs (n=14). Most evaluated monetary incentives for childhood immunisations, particularly conditional cash transfers, while some examined non-monetary incentives including food, mobile phone credit and symbolic rewards. While effect sizes varied substantially across different interventions and contexts, most studies demonstrated modest positive short-term effects on immunisation uptake, and no studies showed decreased uptake. However, several revealed unintended consequences, including reduced intrinsic motivation manifesting as lower immunisation uptake when incentives were withdrawn, creation of payment expectations and implementation challenges affecting acceptability. Several studies highlighted how incentive programmes could undermine community volunteerism and trust in both immunisation and health services, particularly when poorly implemented or withdrawn.

conclusionsWhile incentives can improve short-term immunisation uptake in LMIC, their effects vary by context, and they can have negative unintended consequences which need to be taken into consideration in programme design. Future programmes should be co-designed with communities, consider locally acceptable non-monetary alternatives, incorporate strategies to maintain intrinsic motivation and ensure sustainable implementation within existing health systems.