Veterinarian Patricia Jordan DVM has documented several cases of tumors from the lepto vaccine, especially from combination vaccinations that include leptospirosis. (dogsnaturallymagazine.com)
As for other vaccinations, in my opinion, many of them are given with too many viral / bacterial components in one injection, and many vets routinely give two or three combination vaccinations at one time. (blog.petmeds.com)