Disparities in H1N1 Vaccination Rates: a Systematic Review and Evidence Synthesis to Inform COVID-19 Vaccination Efforts

Background: Data suggest that there were disparities in H1N1 vaccine uptake, and these may inform COVID-19 vaccination efforts. We conducted a systematic review to evaluate disparities in H1N1 vaccine uptake, factors contributing to disparities, and interventions to reduce them. Methods: We searched English-language articles in MEDLINE ALL, PsycINFO, Cochrane Database of Systematic Reviews, and Cochrane Central Register of Controlled Trials from database inception through May 8, 2020. Observational studies examining H1N1 vaccine uptake by race/ethnicity, socioeconomic status, rurality, and disability status in US settings were included. Two reviewers independently assessed study eligibility. Single-reviewer data abstraction was confirmed by a second reviewer. We conducted independent dual quality assessment, and collective strength of evidence assessment. Results: We included 21 studies. African American/Black, Latino, and low-socioeconomic status participants had disproportionately lower H1N1 vaccination rates (low- to moderate-strength evidence). However, Latinos were more likely than Whites to intend to be vaccinated, and African American/Blacks and participants with lower-socioeconomic status were just as likely to intend to be vaccinated as their White and higher-socioeconomic status counterparts (low-strength evidence). Vaccine uptake for other groups has been insufficiently studied. Factors potentially contributing to disparities in vaccine uptake included barriers to vaccine access, inadequate information, and concerns about vaccine safety and efficacy. Studies were largely cross-sectional. Many of the studies are a decade old and were conducted in the context of a different pandemic. The categorization of racial and ethnic groups was not consistent across studies and not all groups were well-studied. Discussion: Efforts to avoid disparities in COVID-19 vaccination uptake should prioritize vaccine accessibility and convenience in African American/Black, Latino, and low-SES communities; engage trusted stakeholders to share vaccine information; and address concerns about vaccine safety and efficacy. Primary Funding Source: Department of Veterans Affairs, Veterans Health Administration, Health Services Research & Development. Protocol Registration: PROSPERO CRD42020187078.