Virus wakes up dormant cells in different way that your immune system. Immune system has many levels of operation and that is why you have different lines of "white" blood cells PLUS immunity on pure biochemical level. Our immune system is supposed to kill off cancer and it does ! It is only when our immune system is not doing its job that we get a cancer, not to mention mets.
Immune system works on very fine biochemical level and can quiet easily distinguish what is a friend and what is foe WHEN it is healthy, strong and functioning correctly.
When it is weak or overactive - we have a problem. In the first case all bad actors proliferate without being eliminated, in another our body overreacts with high level of inflammation that can be deadly (cytokine storm) or one develops autoimmune disease.
Why COVID activates cancer - that is now question that needs further research. It could be that inflammation is so great that our immune system is so overwhelmed and stops keeping mets in check ! OR, some substance that is exuded during that level of inflammation is a motor oil for cancer DNA. Don't forget that COVID virus actually attaches to prostate membrane !!! Now, we have whole line of viruses that are known to CAUSE cancer ! They invade our cells and insert so called oncogenes in our DNA and our cells become cancer cells. The most known one is herpes virus - one that causes genital warts and that is why there is a vaccine for that virus - to prevent uterine and penile cancers.
I think that calling immune-therapy for cancers "vaccination" is wrong, and of course , confusing for general population. They should come up with different terminology . especially nowadays where so many people are anti vaccination.