INTRODUCTION: Community health workers (CHWs) could expand immunization access in under-reached communities by administering vaccines. This rapid review identifies countries where CHWs administered vaccines and synthesizes health systems factors that may contribute to or detract from the feasibility of CHWs administering vaccines. METHODS: We conducted a rapid review of peer-reviewed literature from 3 databases and gray literature identified through web searches and by CHW subject matter experts. We treated extracted data on conditions related to vaccine administration by CHWs as qualitative data and conducted deductive content analysis. RESULTS: We retained 32 documents from 497 initial records and identified 23 CHW cadres that vaccinated in 20 countries, ranging from long-established national programs delivering routine immunizations to pilot projects delivering 1 specific vaccine. CHWs who vaccinate face the following challenges: (1) inadequate supply chain training, (2) inadequate cold chain equipment, (3) transportation for supplies and to communities, (4) heavy existing workload, (5) inadequate or irregular remuneration, (6) inadequate or irregular supervision. CONCLUSION: To improve immunization coverage in underimmunized and zero-dose communities, countries where CHWs vaccinate should provide CHWs with adequate remuneration, supervision, supply chain support and management, and formal integration within the health system. CHWs administered vaccines in 20 of the 75 countries with documented CHW programs, suggesting the majority of an estimated 3.3 million CHWs globally do not yet administer vaccines. In light of health care workforce shortages and immunization equity gaps, further exacerbated by the COVID-19 pandemic, policymakers should consider task-shifting vaccine administration to CHWs to bolster immunization access for under-reached communities. Additional systematic documentation is needed to further explore best practices to support CHWs as vaccinators, especially related to supply chain, policy, safety, and efficacy.