*2.3. Quality Assessment*

Two reviewers (C.P. and J.-Y.C.) independently performed reporting quality assessment using the Consolidated Health Economic Reporting Standard (CHEERS) 2022 statement [21]. Any disagreements during the reporting quality assessment were resolved by consensus upon discussion with the third reviewer (N.C.).

#### *2.4. Data Synthesis*

Following data extraction, we summarized how health equity was incorporated and evaluated in the selected economic evaluations of vaccines, including methodological characteristics, characteristics of vaccines and immunization programs, existing inequities in the health systems, characteristics of equity-relevant subpopulations, and study findings. Equity-relevant subpopulations were categorized following the PROGRESS-Plus framework, including (1) place of residence, (2) race/ethnicity/culture/language, (3) occupation, (4) gender/sex, (4) religion, (5) education, (6) socioeconomic status, (7) social capital, (8) personal characteristics associated with discrimination (e.g., age, disability), (9) features of relationships (e.g., smoking parents, excluded from school), and (10) time-dependent relationships (e.g., leaving the hospital, respite care, other instances where a person may be temporarily at a disadvantage) [22].
