I wonder if mRNA vaccine treatment for cancer is what they are referencing.

From what I was able to understand (and maybe somebody can correct anything I've gotten wrong), the "vaccine" is tailored on a per-individual basis to target key protein markers of a petients particular cancer. This allows the body to identify and start to attack the cancer where previously the immune system would not be able to tell the difference between healthy and cancerous cells.

Ref: https://www.cancer.gov/news-events/cancer-currents-blog/2022/mrna-vaccines-to-treat-cancer