Cancer vaccines come in two very different kinds. Preventive vaccines stop infections that cause cancer — the HPV vaccine prevents most cervical and several other cancers, and the hepatitis-B vaccine lowers liver-cancer risk; these are among the most effective cancer-prevention tools available. Therapeutic (treatment) vaccines aim to stimulate the immune system against a cancer that already exists: examples include sipuleucel-T for advanced prostate cancer and BCG immunotherapy instilled in the bladder for early bladder cancer. Personalized neoantigen and mRNA-based cancer vaccines — tailored to a patient’s own tumor mutations, often combined with checkpoint immunotherapy — are a major area of active clinical research.
Preventive vaccines are routine injections given before exposure. Therapeutic vaccines vary: sipuleucel-T is made from a patient’s own immune cells and infused; BCG is placed directly into the bladder; investigational vaccines are given by injection, usually in a clinical trial and often with other immunotherapy.
Preventive vaccines have well-established safety. Therapeutic vaccines are generally given in courses with monitoring; benefits and side effects depend on the specific product and the cancer.