Couldn't agree more. Like several human vaccines (influenza and COVID-19), reducing severity of illness or even asymptomatic infection is considered a desired outcome.It's unrealistic to expect that a vaccine may 100% prevent an animal from getting the virus at all, but it preventing the symptoms from advancing/becoming lethal is just as much of a success!
I admittedly don't know much about the mutation history of EEHV, but knowing there are several strains, it will be interesting to see how well the vaccine (which at this point is a single strain vaccine) offers protection or reduction in severity of illness of other strains. I wonder if the strain that the Cincinnati boys have is the EEHV1A, which tends to be the more lethal strain in Asian Elephants and the one that this first vaccine was created for.