Background <p>The <i>Plasmodium</i> liver stage is an attractive prophylactic vaccine target since blocking parasites in the liver has the potential to prevent both clinical disease and transmission. However, immunity to <i>Plasmodium</i> liver stages is difficult to study, and highly efficacious liver stage vaccines have been difficult to develop. Prime-and-trap vaccination induces liver CD8⁺ T cells that can provide complete liver stage protection in mice. However, the minimal vaccine requirements for complete liver stage protection remain unclear.</p> Methods <p>In this study, a prime-and-trap vaccination strategy was used to evaluate minimal vaccine requirements for malaria liver stage protection in mice. Here, Prime-and-trap pulls and traps primed <i>Plasmodium yoelii</i> circumsporozoite protein (CSP)-specific CD8⁺ T cells in the liver via liver expression of DNA-encoded CSP delivered by hydrodynamic transfection (HDT). HDT-CSP trapping doses were progressively de-escalated to define the minimal requirements for inducing CSP-specific CD8⁺ T cells in the liver.</p> Results <p>Prime-and-HDT trap induced sterile protection against sporozoite challenge with CSP-HDT doses as low as 5&#xa0;ng DNA. However, protection was lost at an ultra-low CSP-HDT dose of 50&#xa0;pg, which was associated with a similarly low level of CSP-specific CD8⁺ T cells in the liver. These results suggest that there is a threshold of CSP-specific CD8⁺ T cells required in the liver to achieve sterile protection.</p> Conclusions <p>Overall, these studies indicate that prime-and-HDT trap vaccination offers a tractable new strategy to study immunity to liver stage malaria in mice that is inexpensive, reproducible, and accessible.</p>