A number of enteric vaccine candidates are in clinical product development, including those to address the burden of Shigella, enterotoxigenic E. coli, norovirus and invasive non-typhoidal Salmonella. Prioritization and funding across this portfolio are dependant to a large extent on which vaccines could have the greatest impact on public health, informed by the burden of disease, considering the constraints of both the R&D and programmatic delivery environments. Infections with enteric pathogens result in mortality (deaths) and morbidity (malnutrition, stunting, cognitive impairment, other) of which impact can last long after the initial infection took place. To comprehensively assess the Full Value of Vaccines (FVVA) and inform vaccine prioritization and use, both mortality and morbidity need to be explicitly quantified.

Modelling groups such as Institute for Health Metrics and Evaluation (IHME) and Maternal Child Epidemiology Estimation (MCEE) have published mortality estimates for enteric diseases. WHO has undertaken efforts to understand how these mortality estimates were calculated, what type of data were used, what assumptions were made, and what are the research gaps to iterate future estimates⁽¹⁾. Despite the increase in transparency of methodologies to calculate the mortality estimates of enteric infections, there is a lack of consensus on how to measure, analyse and present morbidity associated with enteric infections. As such, WHO analysing evidence on the impact of enteric pathogens on long-term morbidity, including growth faltering and cognitive impairment. Such data will inform estimates about the value of vaccines that avert morbidity, which is currently underestimated. 

References

¹ Butkeviciute E, Prudden HJ, Jit M, Smith PG, Kang G, Riddle MS, et al. Global diarrhoea-associated mortality estimates and models in children:  Recommendations for dataset and study selection. Vaccine. 2021 Jun. Available at: https://www.sciencedirect.com/science/article/pii/S0264410X21006812

Related Publications

• Meeting Report: WHO Workshop on modelling global mortality and aetiology estimates of enteric pathogens in children under five. Cape Town, 28-29th November 2018. Available at: https://www.sciencedirect.com/science/article/pii/S0264410X20300803
• Baker JM, Hasso-Agopsowicz M, Pitzer VE, Platts-Mills JA, Peralta-Santos A, Troja C, Archer H, Guo B, Sheahan W, Lingappa J, Jit M. Association of enteropathogen detection with diarrhoea by age and high versus low child mortality settings: a systematic review and meta-analysis. The Lancet Global Health. 2021 Oct 1;9(10):e1402-10. Available at: https://www.thelancet.com/journals/langlo/article/PIIS2214-109X(21)00316-8/fulltext