A high cell passages canine coronavirus vaccine for the immunization of dogs.

The efficacy of a high cell passages (hcp) canine coronavirus (CCoV) vaccine was evaluated for the immunization of dogs. Three dogs, previously tested and resulted seronegative and virus negative for CCoV, was inoculated twice at 21 days intervals with 4 ml of the hcp-CCoV vaccine and kept under observation for any adverse reactions. Two control dogs, sero- and virus-negative, were maintained non-vaccinated. The safety of the vaccine was tested in two further dogs inoculated by oro-nasal route with 10 times the vaccinal dose. During the observation period these dogs did not display any local or systemic reaction. Following the first and second vaccination, faecal samples were collected daily from the three dogs and fourteen days later the second inoculation the vaccinated and the two controls dogs were challenged with a field CCoV strain. Blood samples for serology were collected at T0 and weekly after vaccinations and after challenge. After the first and the second inoculations, the virus was not detected in faecal samples by both virus isolation (VI) and PCR assay. After challenge, the vaccinated dogs did not display clinical signs and virus shedding was not observed. The two control dogs displayed moderate clinical signs and the virus was detected by VI for 14.5 median days, by PCR assay for 23 median days. The present study has demonstrated the efficacy of the hcp CCoV vaccine in preventing the infection of dogs and, in particular its ability to induce a strong protective and long-lived immunity to infection.