An Inactivated H3N2 Canine Influenza Virus (CIV) Vaccine Aids in the Prevention of Clinical Disease and Virus Shedding in Dogs Challenged with Virulent H3N2 CIV

Canine influenza virus (CIV) is an etiologic agent of canine infectious respiratory disease (CIRD). In March of 2015, a strain of H3N2 subtype CIV, previously found only in Asia, emerged in Chicago, IL, USA. The virus triggered localized outbreaks of CIRD in Illinois, and rapidly spread to dogs in at least 30 different U.S. states. In response to this outbreak and the high probability that current H3N8 CIV vaccines would not prevent disease caused by the newly emergent virus, we developed a monovalent, inactivated H3N2 CIV vaccine. In this study, we evaluated the safety and efficacy of the vaccine and showed that vaccinated dogs were protected from clinical disease and shed less virus following challenge with a virulent H3N2 CIV strain compared to placebo vaccinated dogs. The vaccine was administered subcutaneously, twice, 3 weeks apart, and did not cause adverse systemic or administration site reactions. Collectively, our findings support the use of this vaccine to aid in the reduction of clinical disease caused by H3N2 CIV.