I'm not sure which specific 'cancer vaccine inventor' this refers to. There could be various incidents, but without more context, it's hard to tell the full story.
Well, if we consider the general context of a cancer vaccine inventor being killed, it could potentially be a very tragic situation. In the field of medicine, especially in cancer research, the development of a vaccine is a huge deal. There could be numerous motives behind such a killing. For instance, if a new cancer vaccine was on the verge of a major breakthrough, it might disrupt the market of existing treatments or pharmaceutical companies that have a vested interest in other forms of cancer treatment. Another possibility could be that the inventor had some information that was considered dangerous or threatening to certain parties. However, without specific details about the case, it's extremely difficult to provide a comprehensive and accurate full story.
There may be many cancer vaccine inventors around the world. To accurately answer this question about one being killed, we need to know more details such as the name of the inventor, when and where this happened. Without these key pieces of information, we can only assume that it could be due to a range of reasons like corporate competition, political interference, or personal vendettas in the complex world of medical research and development. But again, this is all speculation without proper information.