There are a lot of concerns about the potential risks of vaccines, including fears that vaccines can cause autism, can infect the recipient with the disease the vaccine is designed to prevent, and are generally unsafe. Rest assured: Vaccination is one of the most convenient and safest preventative care measures available, according to the U.S. Centers for Disease Control and Prevention.

But what’s the deal with preventative vaccines and cancer? Can receiving a vaccine cause cancer? The answer is no: Vaccines do not cause cancer. In fact, there are even types of vaccines, known simply as cancer vaccines, that can prevent or potentially treat cancer.

What are vaccines?

Vaccines are made from very small amounts of weak or dead germs that can cause diseases, such as viruses, bacteria, or toxins. Getting vaccinated sparks a response from your immune system and helps your body fight off and remember the germ, so it can fight the disease faster and more effectively in the future if necessary. Since vaccines contain only very small amounts of the germs, they won’t make you sick.

Are vaccines safe?

All vaccines in the United States are approved by the U.S. Food and Drug Administration (FDA) for safety and effectiveness before they are licensed. The FDA spends years testing vaccines through clinical trials to determine if a vaccine is safe, what dose to administer, and how the immune system reacts to it.

Each batch of a vaccine is also tested for quality and safety to ensure that the vaccine works like it is supposed to, and that it is not contaminated with certain ingredients used during production or outside germs.

The U.S. government also tracks vaccination records [MR1] to monitor and track patient and vaccine safety, as well as to conduct studies about rare and serious adverse events following immunization. For the most part, side effects are minor.

Side effects

Although vaccines are tested thoroughly and continuously monitored, vaccines can still cause side effects. These side effects vary based on the vaccine administered. According to the Centers for Disease Control and Prevention (CDC), the most common side effects can include:

  • Soreness where the vaccine was administered
  • Low-grade fever
  • Fatigue
  • Headache
  • Chills

Serious side effects from vaccines are extremely rare; if a million doses are given, just 1-2 people may have a severe allergic reaction. There is also no evidence that childhood vaccines cause autism.

Do vaccines cause cancer?

There is no link between vaccines and an increased risk of cancer. However, it is generally recommended that cancer patients do not receive vaccines during chemotherapy, immunotherapy, or radiation, except for the flu shot. Vaccines need an immune system response to work properly, and patients undergoing treatment may have a weakened immune system. Infections are also possible if those with weakened immune systems are administered a vaccine with a live virus. Your doctor should tell you about any vaccines that might help you, such as a cancer vaccine.

Cancer vaccines

Cancer vaccines are different from vaccines that work against viruses. There are two types of cancer vaccines: those that can treat cancer, and those that can prevent it.

Treatment vaccines

These cancer vaccines aim to help treat or prevent a recurrence of cancer by attacking cancer cells throughout the immune system. They are made up of cancer cells, parts of cells, or pure antigens – substances that induce an immune response in the body, especially the production of antibodies, proteins produced by the immune system. Sometimes, a patient’s own immune cells are removed and exposed to these substances to create the vaccine.

So far, sipuleucel-T (or Provenge) is the only vaccine in the U.S. approved to treat cancer. It is designed to stimulate an immune response against metastatic prostate cancer and is customized to each individual patient. Researchers are currently testing experimental treatment vaccines in a variety of cancers, including:

  • Melanoma
  • Brain tumors
  • Breast cancer
  • Kidney cancer
  • Leukemia

Current immunotherapy research at Dana-Farber Cancer Institute includes finding ways to make tumors immunologically “hot,” or more likely to provoke an immune system attack on the cancer. Researchers hope to generate more potent and precise attacks on cancer.

Preventative vaccines

Some cancer vaccines may help prevent certain cancers, including:

  • The human papilloma virus (HPV) vaccine. Some strains of HPV are linked to cervical, anal, throat, and other cancers.
  • The hepatitis B (HBV) virus. Long-term HBV infections can increase the risk of liver cancer.

If you’re unsure whether you should be vaccinated, work with your doctor to determine which vaccinations you’ve received and which ones, if any, you might still need. If you’re unsure which vaccinations you’ve already received, you can also contact former doctors and request your immunization records. If your records are unavailable, your doctor can perform a test for evidence of immunity, whether from a prior vaccination or an infection.

This article was originally published on July 25, 2019, by Dana-Farber Cancer Institute. It is republished with permission.