Table 1. Characteristics of studies.

Study	Year	Study setting (country)	Study design	Analysis	Number included	Estimated mean age	Language/cultural appropriateness	Ethnicities, as given by study	Percent female	Vaccine type
Abel [16]	2003	US	Survey	Chi2	1,006	75.2*	No mention but likely English	African American, Caucasian	61.4	Influenza
Albright [17]	2017	US	Focus groups	Team-based process; reflexive team analysis	68	52.1*	English or Spanish	English-speaking, Spanish-language	NS	Diphtheria, influenza, pertussis, pneumococcal, tetanus
CDC [18]	1997	US	Telephone survey	NS	600	NS	English or Spanish	Hispanic, White, other	NS	Influenza, pneumococcal, tetanus
Armstrong [19]	2001	US	Telephone survey	Chi2, log regression	486	76.6	No mention but likely English	African American, Caucasian, Hispanic	71.1	Influenza
Cameron [20]	2009	US	Focus groups	Extended parallel process model, latent content, and constant comparative techniques	48	74.1	No mention but likely English	African American	87.5	Influenza
Casarin [21]	2011	Brazil	Semi-structured interviews	Thematic analysis	7	69.4	Brazilian Portuguese	NS	57.1	Influenza
Chen [22]	2020	US	Telephone survey	Chi2, log regression	1,961	58.8	English or Spanish	Black, Filipino, Japanese, Latino, White	65	Influenza
Harris [23]	2006	US	Semi-structured in-depth interviews	Content analysis, including triangulation and constant comparison approach	20	71.5** (vaccinated); 74.0** (unvaccinated)	No mention but likely English	African American	70	Influenza, pneumococcal
Hebert [24]	2005	US	Survey	Logistic regression	6,746	74.5	No mention but likely English	African American, Hispanic, White	58.2	Influenza
Kajikawa [25]	2019	Japan	Questionnaire	Logistic regression	316	75**	Japanese	Japanese	48.4	Influenza
Kwong [26]	2008	Hong Kong, China	Survey	NS	70	75.8*	Chinese, likely Cantonese	Hong Kong Chinese	51.4	Influenza
Kwong [27]	2009	Hong Kong, China	Questionnaire	Chi2, t test, Kolmogorov–Smirnov test, logistic regression	197	75.2*	Chinese, likely Cantonese	Chinese	58.9	Influenza
Kwong [28]	2010	China, Indonesia, Turkey, South Korea, Greece, Canada, UK, Brazil, and Nigeria	Focus groups	Thematic analysis	208	75.5*	English and multiple non-English languages (not specified)	Multiple—Chinese, Indonesian, Turkish, Korean, Greek, Canadian, British	62.8	Influenza
Lasser [29]	2008	US	Survey and observation	Qualitative analysis	18	71.9	English or Spanish or Haitian Creole	Black, mixed, other, White	77.8	Influenza
Lau [30]	2008	Hong Kong, China	Telephone survey	Chi2, logistic regression	483	75.5*	NS	Hong Kong Chinese	55	Influenza
Nowalk [31]	2006	US	Telephone survey	Chi2, logistic regression	375	64.9*	English	African American	63	Influenza, pneumococcal
Phippard [32]	2013	US	Survey	Chi2, logistic regression	197	46.5*	English or Spanish (culturally appropriate)	Mexican	70.1	Influenza
Ramanadhan [33]	2015	US	Online survey	ANOVA, Chi2	1,569	44*	English	African American, Hispanic	56	Influenza
Rikin [34]	2017	US	Survey	Wilcoxon, logistic regression	200	74	English or Spanish (culturally appropriate, with translators)	Hispanic	73	Influenza
Schwartz [35]	2006	US	Survey	Chi2, logistic regression	454	77.5*	English	African American	54.4	Influenza
Sengupta [36]	2004	US	Interviews	Thematic coding	28	74.9	English	African American	78.6	Influenza
Singleton [37]	2005	US	Survey	Chi2, log regression	1,839	77.6*	English	Black, Hispanic	58.6	Influenza, pneumococcal
Siu [38]	2021	Hong Kong, China	Interviews	Thematic coding	40	72.7	Cantonese	Hong Kong Chinese	67.5	Influenza, pneumococcal
Sun [39]	2020	Hong Kong, China	Survey and focus groups	Chi2, log regression	2,452	51.4*	Cantonese	Hong Kong Chinese	64.8	Influenza
Takahashi [40]	2003	Japan	Case–control	Chi2, t test, Mann–Whitney, logistic regression	210	69.8	No mention but likely Japanese	Japanese	66.7	Influenza
Winston [41]	2006	US	Telephone survey	Chi2, multivariate binomial regression	4,577	74.5	No mention but likely English	Black, Hispanic, White	Unknown; ‘majority’ stated	Influenza, pneumococcal
Wooten [42]	2012	US	Telephone survey	Chi2, logistic regression	3,821	77.8*	No mention but likely English	Black, Hispanic, other, White	64.7	Influenza, pneumococcal
Yu [43]	2014	Hong Kong, China	Questionnaire	Logistic regression	306	74.6	Chinese, likely Cantonese	Chinese	37.9	Influenza

*Mean age estimated using sum total of each subgroup frequency multiplied by mid-point of each range divided by total frequency.

**Median age used.

ANOVA, analysis of variance; CDC, Centers for Disease Control and Prevention; NS, not stated.