A cancer vaccine is a vaccine that either treats existing cancer or prevents the development of cancer. Vaccines that treat existing cancer are known as therapeutic cancer vaccines. American Society of Clinical Oncology (ASCO), the leading medical professional oncology society, is committed to lessening the burden of cancer and as such will promote underused interventions that have the potential to save millions of lives through cancer prevention. It’s generally recommended that vaccines not be given during chemo or radiation treatments – the only exception to this is the flu shot. This is mainly because vaccines need an immune system response to work, and you may not get an adequate response during cancer treatment. People with weak immune systems can get some vaccines, but they should not get any vaccines that contain live virus. Two hundred seventy-three medical oncologists participated in the survey. Influenza, Pneumococcus, and Hepatitis B were the most commonly recommended vaccines. Patients with lung cancer, lymphoma, and breast cancer were the main malignancies that medical oncologists suggest vaccination.