Vaccination was a key measure to tackle the Covid-19 pandemic, however adolescents were less likely than adults to accept the vaccine. Low vaccine uptake reduces the effectiveness of vaccination campaigns and threatens global public health. Understanding why adolescents are hesitant to accept new vaccines is therefore crucial to support the development of novel vaccine uptake interventions. Prior reviews have included far fewer citations, excluded qualitative data, studies after 2022 and have not mapped adolescent Covid-19 vaccine behaviour onto psychological models. This systematic review investigates psychological factors influencing attitudes and intentions toward and uptake of Covid-19 vaccines in adolescents aged 10 to 19 years globally. Next, we mapped results onto the COM-B framework to inform future interventions. Our search identified 25,354 citations, and included 77 in this review. The quality of studies was mixed, predominantly cross-sectional in design. According to our review, key influences on adolescent Covid-19 vaccine behaviour were: i) Reflective motivation (safety concerns, perceived susceptibility to/severity of Covid-19, perceived vaccine effectiveness, ii) Social opportunity (social norms, autonomy and prosocial attitudes), iii) Psychological capability (attitude and knowledge about vaccines). To improve vaccine uptake, interventions should help adolescents critically weigh vaccine pros and cons and consider external influences on their decisions. IMPLICATIONS AND CONTRIBUTION Our review provides new insights into psychological factors influencing adolescent Covid-19 vaccine behaviour, and maps factors to the COM-B model of behaviour change. To improve vaccine uptake, future vaccine interventions should support adolescents to think critically about the pros and cons of vaccines and consider external influences on their decisions.

LES and RA are employees of UK Health Security Agency. GJR and LES receive consultancy fees from the Sanofi group of companies and other life sciences companies. LES, RA, and GJR were participants in the UK Scientific Advisory Group for Emergencies or its subgroups in responding to COVID-19. CH is Director of Health Improvement at Director of Health Improvement at Southwest London Integrated Care Board.

APs PhD is funded by the UK Health Security Agency. This study was funded by the National Institute for Health and Care Research Health Protection Research Unit (NIHR HPRU) in Emergency Preparedness and Response, a partnership between the UK Health Security Agency Kings College London and the University of East Anglia. The views expressed are those of the author(s) and not necessarily those of the NIHR, UKHSA or the Department of Health and Social Care. For the purpose of open access, the author has applied a Creative Commons Attribution (CC BY) licence to any Author Accepted Manuscript version arising.

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