Measuring vaccine effects on antibiotic use and antimicrobial resistance in low and middle-income countries: A scoping review of methodological approaches, data sources, metrics, and limitations

Vaccines represent a critical strategy for combating antimicrobial resistance (AMR), yet methodological approaches for assessing their impact remain heterogeneous, particularly in low- and middle-income countries (LMICs) where both infectious disease and resistance burdens are highest. This scoping review systematically mapped the methodological approaches, data sources, and outcome measures used to evaluate vaccine impacts on AMR in LMICs. We searched PubMed, Web of Science, Scopus and CINAHL for studies examining vaccine-AMR relationships in LMICs. Two reviewers independently screened studies and extracted data on study designs, data sources, outcome measures, and limitations. We followed Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews guidelines. Sixty-two studies met inclusion criteria, including 58 primary studies and 4 reviews. Among primary studies, 45 were observational (72.6%), 11 were modelling studies (17.7%), 2 randomized trials (3.2%), and 4 systematic reviews (6.5%). Evidence concentrated heavily on pneumococcal conjugate vaccines, with minimal research on other WHO priority pathogens. Data sources included surveillance networks, carriage surveys, national reference laboratories, and administrative immunization records. Primary outcome measures included resistance prevalence (n = 58), serotype replacement (n = 18) and antimicrobial use data (n = 23) such as antibiotic prescriptions or defined daily doses. Common limitations included surveillance biases, incomplete vaccination records, single-site generalizability constraints, and limited linkage between microbiological and clinical outcomes. Substantial methodological heterogeneity characterizes vaccine-AMR research in LMICs, with systematic gaps in antimicrobial use data and evidence beyond pneumococcal vaccines. Strengthening digital health infrastructure, integrating antimicrobial use measurements into existing surveys, embedding resistance endpoints in vaccine trials, and standardizing outcome definitions across studies are essential to generate policy-relevant evidence for immunization programs in high-burden settings.