BACKGROUND: Despite measures to reduce young people's access to electronic cigarettes (ECs), or "vapes", many countries have recorded rising youth vaping prevalence. We summarised studies documenting how underage youth in countries with minimum age sales restrictions (or where sales are banned) report accessing ECs, and outline research and policy implications.

METHODS: We undertook a focused literature search across multiple databases to identify relevant English-language studies reporting on primary research (quantitative and qualitative) and EC access sources among underage youth.

RESULTS: Social sourcing was the most prevalent EC access route, relative to commercial or other avenues; however, social sourcing dynamics (i.e., who is involved in supplying product and why) remain poorly understood, especially with regard to proxy purchasing. While less prevalent, in-person retail purchasing (mainly from vape shops) persists among this age group, and appears far more common than online purchasing.

CONCLUSIONS: Further research examining how social supply routes operate, including interaction and power dynamics, is crucial to reducing youth vaping. Given widespread access via schools and during social activities and events, exploring how supply routes operate and evolve in these settings should be prioritized. Inadequate compliance with existing sales regulations suggest greater national and local policy enforcement, including fines and licence confiscation for selling to minors, is required at the retailer level.