**5. Conclusions**

In this scoping review, we assessed 167 research articles to provide an overview of how within-country COVID-19 vaccination coverage inequality has been studied. Our findings demonstrate that most research to date has been conducted in higher income countries, underscoring the need for expanded research in other contexts to gain a fuller understanding of patterns of inequalities across populations and settings. While we characterised research on diverse dimensions of inequality, those most frequently studied were related to demographic factors. The trends that we reported for inequalities by age, race/ethnicity/cultural group/language/nationality/country of birth, and sex/gender dimensions of inequality were intended to be preliminary and exploratory. More detailed analyses across these and other dimensions of inequality are warranted, including dedicated systematic reviews and meta-analyses to draw more reliable and specific conclusions. Research in this topic area can be further strengthened by adopting standardised COVID-19 vaccination indicators, which would promote greater cross-study comparability.

As COVID-19 vaccination programmes, including the administration of booster doses, continue to expand globally, ongoing efforts are needed to grow this body of research and capture the evolution of inequalities in vaccination coverage, both globally and locally within countries. The characterisation of inequalities related to multiple, diverse dimensions of inequality (encompassing both context-specific and universally applicable dimensions) stands to offer relevant lessons and insights for strengthening equity in vaccine policies, planning and implementation.

**Supplementary Materials:** The following supporting information can be downloaded at: https:// www.mdpi.com/article/10.3390/vaccines11030517/s1, S1: Scoping review protocol. This document contains the protocol that was followed in conducting the scop-ing review. It indicates where modifications and clarifications were made to the initial protocol; S2: Search terms. This document contains the terms used to conduct systematic searches within PubMed, Scopus and Web of Science; S3: Study sources. This document contains information about the journals where sourced articles were published. Table S1: Number of articles included in a scoping review about inequalities in COVID-19 vaccination coverage, by journals where pub-lished. Refs. [13,14,52] are cited in Supplementary Materials.

**Author Contributions:** Conceptualisation, N.B. and A.R.H.; study selection and data extraction—N.B. and N.E.J. with guidance from A.R.H.; writing—original draft, N.B.; writing—review and editing, N.B., N.E.J., D.C.B. and A.R.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Gavi, the Vaccine Alliance.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** A list of the articles included in the review is available upon request from the authors.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
