A large-scale field randomized trial demonstrates safety and efficacy of the vaccine LetiFend® against canine leishmaniosis.

Canine leishmaniosis is a zoonotic disease caused by Leishmania infantum. Extensive research is currently ongoing to develop safe and effective vaccines to protect from disease development. The European Commission has granted a marketing authorization for LetiFend®, a new vaccine containing recombinant Protein Q. The efficacy of LetiFend® vaccination in a large-scale dog population of both sexes, different breeds and ages in endemic areas is reported in this multicenter, randomized, double-blind, placebo-controlled field trial. Dogs (n = 549) living in France and Spain were randomly selected to receive a single subcutaneous dose of LetiFend® or placebo per year, and were naturally exposed to two L. infantum transmission seasons. Clinical examinations, blood and lymphoid organ sampling to evaluate serological, parasitological and disease status of the dogs were performed at different time points during the study. LetiFend® was very well tolerated and clearly reduced the incidence of clinical signs related to leishmaniosis. The number of confirmed cases of leishmaniosis was statistically significantly lower in the vaccine group. The number of dogs with parasites was close to be significantly reduced in the vaccine group (p = 0.0564). Re-vaccination of seropositive dogs demonstrated to be safe and not to worsen the course of the disease. The likelihood that a dog vaccinated with LetiFend® develops a confirmed case or clinical signs of leishmaniosis in areas with high pressure is, respectively, 5 and 9.8 time less than that for an unvaccinated dog. Thus, the overall efficacy of the LetiFend® vaccine in the prevention of confirmed cases of leishmaniosis in endemic areas with high disease pressure was shown to be 72%. In conclusion, this field trial demonstrates that LetiFend® is a novel, safe and effective vaccine for the active immunization of non-infected dogs from 6 months of age in reducing the risk of developing clinical leishmaniosis after natural infection with Leishmania infantum.