The adjuvant access problem: barriers to broader vaccine development

Abstract

Vaccine development increasingly depends on adjuvants, particularly for antigen-based platforms that require immune enhancement to achieve protective efficacy. Vaccine adjuvants do more than boosting humoral responses; they can also enable antigen dose-sparing and promote Th1-skewed cellular immunity needed for intracellular pathogens and difficult vaccine targets. Yet access to potent adjuvants, including MF59, Matrix-M, and the GSK AS-series, remains highly restricted. This is not simply the result of intellectual property (IP) rights, but also overlapping structural barriers, including trade secrets, confidential know-how, selective licensing and supply arrangements, and developmental costs. These constraints disproportionately affect low- and middle-income country (LMIC) manufacturers and smaller vaccine developers, who are often pushed towards aluminium salts as a commercial default. Initiatives such as adjuvant screening libraries, non-exclusive access models and technology-transfer programs show that broader access is possible, but usually through structured and supported arrangements rather than routine market availability. This commentary argues that adjuvant inequity is not an incidental gap in the vaccine ecosystem, but a predictable outcome of current regulatory, commercial and manufacturing structures. Drawing on regulatory guidance, real-world licensing and supply arrangements, pandemic-era vaccine experience, access-oriented initiatives, and emerging evidence on cost, supply and scalability, it shows that broader access is possible but remains selective, originator-controlled, and difficult to scale. Addressing these barriers will require governance models that preserve incentives for originator-led innovation while improving access, affordability, and the ability of LMIC manufacturers and smaller developers to build on clinically validated adjuvant technologies through more transparent and structured access mechanisms.