Repeated EHV vaccination <90 days apart can result in decreasing antibody levels.
A novel EHV-1 Multiplex assay improves EHV-specific antibody quantification.
EHV vaccination using an inactivated vaccine induced predominately IgG1 and IgG4/7 antibodies.
EHV vaccination also induced IFN-γ production via Th1-cells but not by CD8+ cells.
Repeated EHV vaccination protocols and immune parameters should be re-evaluated to optimize protection.