The recent efforts to mount an R&D response to public health emergencies of international concern have led to the formation of what we term a biochemical infrastructure of vaccine development and production. In principle, this infrastructure is expected not only to curtail existing pandemics but also anticipate and contain yet-to-emerge future threats. Critically, by nature of its geographical distribution and technical modularity that infrastructure promises both to accelerate and expand access to essential medical tools, and in so doing, redress global health inequities. In practice, however, the biochemical infrastructure of vaccines remains highly uneven, fragmented and unjust. Moving beyond calls for ‘global health solidarity’, this paper examines the key actors, normative techniques and socio-technical assemblages, from viral platform technologies to intellectual property waivers and from accelerated regulatory pathways to advance market commitments, that serve to link ‘just-in-case’ and ‘just-in-time’ modalities of global health R&D. We argue that the biomedical infrastructure of vaccine development and production emerging in the wake of the COVID-19 pandemic is unfolding across an innovation ecosystem that is more-than-national and yet less-than global: a reconfiguration that may offer possibilities for a new, radically-overhauled, model of vaccine equity.