Monitoring strategies after the incorporation of vaccines into national immunization programs: a systematic review

The 2030 Immunization Agenda envisions a global landscape where everyone can equally access the benefits of both new and existing vaccines by expanding equitable coverage. Post-introduction evaluation strategies are essential to ensure efficient and rational use of resources invested in immunization programs. However, a notable gap remains in the literature on how these strategies are applied in low- and middle-income countries. This study identify the main strategies used worldwide to monitor vaccines after their incorporation into immunization programs.

This systematic literature review was conducted in accordance with the Cochrane Handbook for Systematic Reviews of Interventions and reported following PRISMA guidelines. Studies were retrieved from PubMed (MEDLINE), Web of Science, Core Collection, SCOPUS, and EMBASE (Elsevier) databases. The review included studies on vaccine monitoring after incorporation into immunization programs, with no date restrictions. Excluded were narrative and systematic reviews, meta-analyses, letters, book chapters, posters, COVID-19 vaccine studies, non-human vaccination research, and studies assessing general impact without post-introduction monitoring.

The search identified 4812 citations, with 1477 duplicates removed. After screening 3335 titles and abstracts, nine studies met the inclusion criteria. While the concept of post-introduction monitoring strategies remains poorly defined, the studies revealed that such monitoring can be performed through evaluation of surveillance systems, economic assessments, and adapted analytical tools. Sentinel surveillance, involving healthcare workers and services, was the most frequently reported strategy, followed by synthetic control methods, pre- and post-introduction comparisons, and use of a World Health Organization tool.

Despite the absence of a standardized framework for post-introduction vaccine monitoring, existing studies demonstrate that evaluations can address effectiveness, safety, coverage, and cost. Beyond epidemiological significance, the incorporation of vaccines into immunization programs provides an opportunity to strengthen policies, promote workforce development, and foster social mobilization in support of vaccination.