Despite the growing vaccine availability, it is not clear how long the protection of COVID-19 vaccines may last. For example, the protection of most flu vaccines only last for 6 months. In addition, vaccines usually are less effective in the elderly due to immunosenescence. Our goal is to address these unmet medical needs by promoting the long-term immunity, which will benefit hundreds of millions of people. With the support of the CIRM COVID-19 seed funding, we have demonstrated that our biomaterial-based vaccine booster can induce the formation of mouse and human T memory stem cells (TMSCs) in vitro and effectively induce TMSC formation in adult and aged mice in addition to the production of neutralizing antibodies. We have also simplified the vaccine booster components for clinical translation. This vaccine booster is an injectable biomaterial-based delivery platform that is scalable for manufacturing, stable for storage, injectable for co-delivery with regular vaccine shots, and adaptable to different vaccine formulations.