Review 2: "The Potential Health and Economic Impacts of New Tuberculosis Vaccines under Varying Delivery Strategies in Delhi and Gujarat, India: A Modelling Study"

RR:C19 Evidence Scale rating by reviewer:

• Potentially informative. The main claims made are not strongly justified by the methods and data, but may yield some insight. The results and conclusions of the study may resemble those from the hypothetical ideal study, but there is substantial room for doubt. Decision-makers should consider this evidence only with a thorough understanding of its weaknesses, alongside other evidence and theory. Decision-makers should not consider this actionable, unless the weaknesses are clearly understood and there is other theory and evidence to further support it.

***************************************

Review:

A new TB vaccine or a revaccination with BCG could be impactful and cost-effective in Delhi and Gujarat, two states in India to reduce the burden of disease of TB.

As written it does not follow the iDSI reference case guidelines for reporting or the CHEERS checklist. There are no details on how incremental costs were calculated. Consequently, I don't feel I have enough information to assess how the model estimated impact, and how costs were estimated, and hence the findings and discussion are hard to verify without more information. I checked if there was an appendix that could provide any additional information and did see reference to one in the paper's methods section or as part of the paper I accessed.

Additionally, the papers objectives are not clearly stated. Page 2 par 3-4 jumps from background to using a mathematical model, but never clearly describes the paper’s intent. Therefore, it is hard to follow the conclusions. For example, from the abstract there is a recommendation to obtain age specific regional estimates of infection prevalence, which are inputs to the model. Similarly the authors call for more evidence on effect and effectiveness, which are also inputs to improve estimates of impact. If an objective of the paper is to identify gaps in information for models to inform national vaccine strategies, these findings would make sense. However, these recommendations don't fall out of the model per se, and these recommendations cost money for more research to obtain inputs for mathematical modeling--so not really clear if this is one of the messages of the paper. Alternatively are the authors trying to use mathematical models to provide information to allocate scarce resources more efficiently in a country the size of India, and one that has a high burden of disease with a lot of heterogeneity across states? Clearly defining the research objectives will also help to assess the methods, results and discussion.