Another kind of cancer vaccine increases the number of white blood cells. Still another type of cancer vaccine attaches bacteria to cancer cells. When the immune system attacks the bacteria, it kills the cancer cells, too. One new cancer vaccine helps the immune system kill problem cells before they even become cancer. These cells are destroyed before they can cause damage.
Most vaccines work by preventing disease.
For example, when you were younger, you were vaccinated against measles. The vaccine has kept you from getting measles. However, cancer vaccines are given to people who already have cancer. These vaccines destroy cancer cells and help prevent the cancer from returning. Scientists are still testing cancer vaccines.