Background: Migrants in Europe are at risk of under-immunisation and may also have lower COVID-19 vaccination intent and uptake. There is an urgent need to better understand the drivers of uptake in these groups to inform the development of migrantsensitive interventions for COVID-19 vaccination and routine vaccination beyond the pandemic. Methods: We did a systematic review (PROSPERO: CRD42020219214) following PRISMA guidelines to explore factors influencing vaccine uptake in migrants in the EU/EEA and identify determinants of under-immunisation. We also held 3 participatory workshops with multinational migrant community leaders (n = 23) in London, to explore solutions and approaches to strengthen COVID-19 vaccine roll-out. Results: We included 66 papers reporting data on 262,761 migrants in the review. Numerous access-related factors (e.g. government policy, communication barriers) influenced uptake. Vaccine hesitancy was attributed to lack of information, concerns