I’ve lost two relatives to that. Soon after getting boosted, both had cancers appear all over the body. Multiple organs, brain, etc. Both gone in a few weeks of discovery despite frantic surgeries.
I know a gal who was in remission and got the vax. The follow-up MRI showed cancer lit up everywhere like a city at night. She passed last year.
A guy on my street is just starting treatment for cancer he beat many years ago.