Concurrent administration of an intranasal vaccine containing feline herpesvirus-1 (FHV-1) with a parenteral vaccine containing FHV-1 is superior to parenteral vaccination alone in an acute FHV-1 challenge model

The administration of intranasal (IN) or subcutaneous (SC) vaccines containing modified live feline herpesvirus 1 (FHV-1) offers some level of protection against FHV-1 challenge, but relative efficacy is <100%. In this study, clinical signs and viral shedding in kittens were compared among three groups: (1) kittens vaccinated concurrently with IN and SC vaccines containing FHV-1 (Group 1, n = 8); (2) kittens vaccinated with a SC FHV-1 vaccine alone (Group 2, n = 8), and (3) unvaccinated control kittens (Group 3, n = 8). All kittens were FHV-1 naïve at enrolment, and challenge with a virulent strain of FHV-1 was performed 1 week after vaccination. Daily clinical signs and pharyngeal FHV-1 shedding were recorded over a 21-day infection period. Overall, kittens in Group 1 had significantly less severe clinical illness than those in Group 2 (P < 0.05). Additionally, significantly less FHV-1 DNA was detected on pharyngeal swabs from kittens in Group 1 compared to those in Group 2 (P < 0.001). Concomitant administration of IN and SC FHV-1 vaccines was superior to administration of the SC FHV-1 vaccine alone in this challenge model of FHV-1 naïve kittens.