Core-shell microcapsules compatible with routine injection enable prime-boost immunization against malaria with a single shot

Inadequate booster uptake threatens the success of immunization campaigns as seen with the recently rolled-out R21 malaria vaccine. The ability to administer both prime and boost immunizations with a single injection would therefore save lives and alleviate healthcare burdens. We present a platform for delayed delivery of the booster dose that is scalable with existing technology, easily injectable, and protective against malaria in vivo. Using chip-based microfluidics, we encapsulated the R21 malaria vaccine in polymer microcapsules that release their content weeks to months post-injection. Co-injecting microcapsules with the priming dose of the R21 vaccine elicited strong antibody responses in a mouse model and provided 85% of the protection of a standard prime-boost schedule. If confirmed in humans, these results would pave the way for rapid deployment of single-shot prime-boost vaccination, an urgently needed global health intervention.