Table 4 Challenges encountered during S-PROTECT and research roadmap

Methodological

Study population uncertainties in terms of TB patients covered by social protection and extent of mixing between social protection beneficiaries and general population

Additional epidemiological analysis are needed to characterise the target populations of specific CTIs, in relation to the broader populations in which those individuals live. Furthermore, it will be important, in a given setting, to characterise better the poverty profile of TB patients compared to the general population: understand the extent to which they overlap, in which way the differ, how this can influence their likelihood to be seen and targeted by cash transfers schemes, as well as this can predict their response to CTIs.

No consensus on rules for data harmonisation across different levels and unit of measures

It will be key to identify appropriate ways to standardise the outcomes and units of measure used across impact evaluation and epidemiological studies, so that they can be appropriately utilised in any future research work on the relationship between development and TB. This effort should be linked to the establishment of an open data portal containing reliable and coherent effect estimates for at least some of the identifiable pathways. Considering the vast and diverse literature involved, such an effort is too ambitious for S-PROTECT alone and should become an independent objective of a broader initiative on social protection and TB (and health in general)

Conceptual

Only 13 pathways were taken into account: only using a materialistic perspective

Other aetiologic models should be considered. For example, using a psychosocial framework, it could be argued that CTIs may reduce levels of stress in a population or even improve their mental health, which in turn may improve individuals’ immunological function and thus risk of TB infection and reactivation, as well as the way children respond to BCG vaccine. From a life-course perspective, it is indeed possible that at least much of the preventive effect of CTIs on TB may not be measureable in adults benefiting from CTIs today, but on adults that have benefitted from CTIs while they were children. It is increasingly acknowledged that the most damaging effects of poverty on health happen during childhood and today CTIs are mainly targeted at children to break the inter-generational transmission of poverty and to reduce this damaging effect of poverty of the physical and mental development of children [19]. It can be argued that this can also apply to TB in terms of risk of TB infection, risk of progression to TB as an adult, and also risk of childhood TB [39]. Future work could implement a life course model [28] to represent CTIs effects on factors such as malnutrition and children’s immune system development [40] and changes in TB exposure over a lifetime [41], while capturing dynamic population age-shifts in incidence [42].

To understand further the plausibility of these alternative pathways, their measurability and how they can be best incorporated into TB modelling efforts, it will be important to expand further the interdisciplinary nature of S-PROTECT, and engage with experts from other disciplines possibly as part of social protection research networks operating under the same framework and scope, such as the recently established Social Protection Action Research and Knowledge Sharing (SPARKS) network.

Only 13 pathways were taken into account: issues of generalisability

S-PROTECT efforts need to replicated and adapted to settings other than Brazil to account for both a context-specific social protection environment and different TB epidemic profile.