The coronaviruses (CoV) such as Middle East respiratory syndrome (MERS)-CoV and severe acute respiratory syndrome (SARS)-CoV "have crossed species to cause severe human respiratory disease."
New study in Immunity tested vaccine design based on Venezuelan equine encephalitis replicons (VRP) encoding a SARS-CoV CD4+ T cell epitope derived from nucleocapsid (N) protein of SARS-CoV (N353). VRPs are non-replicating viral vectors that preferentially "infect human and mouse dendritic cells and serve as self-adjuvants". The N protein is "conserved among different coronaviruses" and unlike highly variable S protein, it could induce cross-protection at T cell level.
Interestingly, when tested on laboratory mice, protection from lethal disease [upon challenge] was nearly complete after i.n. (intra-nasal) but not s.c. (subcutaneous) administration of VRP-SARS-N vaccine, demonstrating the importance of the route of vaccination.
I reviewed this paper to emphasize that "route of vaccination" that induces antigen-specific T cells residing at the port of [pathogen] entry is crucial in vaccine effectiveness.