Background: Despite investments by the Nigerian government and international organizations in childhood immunization to combat child mortality, coverage in many northern states remains below the national average, thereby increasing the risk of vaccine-preventable diseases. This study describes the barriers to immunization in six states in Northeast and Northwest Nigeria, which have the lowest vaccination coverage rates in the country. Method: The socioecological framework informed the design of focus group discussions that we conducted with 93 caregivers and 91 community influencers from March to July 2022 to understand their perceptions of the barriers to immunization uptake. We thematically analyzed data that were inductively and deductively coded in NVivo version 12 software. Results: Supply-side service delivery challenges were the main systems-level barriers to vaccine uptake. These included poor provider attitude, shortage of health workers, vaccine stock-out, long wait- times, and inequitable service delivery. Other barriers were, rumors, misconceptions, vaccine distrust, socio-cultural and religious norms at the community level, and spousal and family disapproval at the interpersonal level. Limited autonomy and mobility, poor vaccine knowledge and awareness of immunization benefits, and concerns about side effects were important individual-level barriers. Conclusion: Strategies for improving immunization uptake should include intensifying community sensitization, improving the numbers and quality of the health workforce, involving men and traditional institutions through context-appropriate channels, and addressing socio-cultural norms and concerns about adverse events after immunization.

The authors have declared no competing interest.

The authors disclose receipt of the following financial support for the research authorship and/or publication of this article. This study was supported by the Bill and Melinda Gates Foundation via an award to evaluate the foundations investment in routine immunization and primary healthcare in Bauchi Borno Kaduna Kano Sokoto and Yobe states. This article contents are solely the responsibility of the authors and do not necessarily represent the views of the Bill and Melinda Gates Foundation.

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Ethical approval was granted by the National Health Research Ethics Committee (NHREC/01/01/2007-17/01/2022) all six states ethical committees (Bauchi (NREC/03/11/19B/2021/10) Borno (073/2021) Kaduna (MOH/ADM/744/VOL.1/1171) Kano (SHREC/2022/3078) Sokoto (SKHREC/016/2022) and Yobe (MOH/GEN/747) and the Population Council Institutional Review Board in New York (Protocol number 992)

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