*3.2. Study Characteristics*

Characteristics of the included studies are summarized in Tables 1 and 2, as well as Table S4 in the Supplementary Materials. Studies were performed in many regions of the world, with most studies conducted in Sub-Saharan African countries (*n* = 8, 38%) [6–8,11,12,23,24,33], and six of them were performed in Ethiopia [6–8,11,12,33]. A large proportion of studies focused on vaccination programs in low- and middle-income countries (LMICs) (*n* = 17, 81%) [6–13,23,24,27–30,33–35]. These studies included a total of 11 antigens, of which rotavirus was commonly evaluated (*n* = 11, 52%) [10,11,13,23,27–30,33–35], followed by human papillomavirus (HPV) (*n* = 5, 24%) [9,12,25,26,35] and *Streptococcus pneumoniae* (*n* = 4, 19%) [8,31,32,35]. Rotavirus vaccine was the most commonly studied in LMICs (11 out of 17 studies, 65%) [10,11,13,23,27–30,33–35], while HPV vaccines [25,26] and pneumococcal vaccination [31,32] (two out of four studies, 50% each) were the most commonly studied vaccines in HICs. The breakdown of antigen by income economy is shown in Table S5 in the Supplementary Materials.


#### **Table 1.** Summary of included studies.

Note: \* Number of studies may not add up, as some included multiple vaccines. † Malaria vaccine (RTS,S/AS01).

#### **Table 2.** Methodological characteristics of included studies.


#### **Table 2.** *Cont.*


Abbreviations: DALY—disability-adjusted life year; HALY—health-adjusted life year; OOP—out-of-pocket; QALY—quality-adjusted life year. Note: \* Number of studies may not add up, as some used multiple approaches. † Perspective was categorized based on authors' statements in the articles or reviewers' judgment based on methodologies of the studies. ‡ Two studies also estimated financial risk protection as household OOP expenditures averted as a percentage of household income. § Distributional effect of herd protection was estimated across subpopulations.
