This is hotter than a thirst trap btw
I can answer this.
For a vaccine to work, you need to know a specific target that differentiates the malignancy from the healthy parts of your body.
For cancer and the common cold, there are too many targets for one silver bullet vaccine to be developed for everyone. For HIV the mechanism of infection is such that it makes eradicating the virus completely nearly impossible.
For Covid, nearly everyone was infected with a virus that contained the spike protein, which is found no where else in the body. This was the universal target that the vaccine was developed to identify.