Neoplasia may be seen as early as six weeks following vaccination, and we have seen it occur even in young cats after a single vaccination. Overall, however, there is no age predilection.
Dogs get post-vaccinal granulomas, but no neoplastic transformation has been reported.
Most reported cases have followed vaccination for rabies, but some have been in cats that have received only leukemia vaccine. It is likely that any vaccine can induce the tumor, and virtually all brands have been implicated. For these reasons, it seems likely that it is NOT the antigen per se, but some component of the vaccine vehicle that causes the tissue irritation that leads to eventual neoplastic transformation. These are very rapidly progressive, locally invasive neoplasms that are difficult to cure. The original tumor often seems to be reasonably well circumscribed and amenable to cure by excision, yet even these examples frequently recur at the surgical site within a few months.