Vaccines protect you from many potentially serious diseases. They work by introducing the body to a disease-causing germ, known as a pathogen. This allows the immune system to build a response that can protect you from that pathogen in the future.

If you’ve had chemotherapy for cancer, you may have heard that you can’t get certain vaccines.

In this article, we discuss why this is, which vaccinations are recommended, and the benefits and risks associated with them.

Chemotherapy works by killing fast-growing cells in your body. While many of these cells are cancer cells, others are healthy cells, including cells in the bone marrow.

The bone marrow makes blood cells, including white blood cells (WBCs). WBCs are a vital part of your immune system. Drops in WBCs due to chemotherapy can weaken your immune system.

While standard chemotherapy doesn’t completely wipe out the protection provided by vaccines, it can lead you to generate a weaker immune response to them. This can mean that vaccines may be less effective for you than for a healthy person.

If you’re undergoing myeloablative chemotherapy, you’ll typically need to be revaccinated. That’s because this form of chemotherapy removes vaccine protection. Myeloablative chemotherapy is given to eradicate the bone marrow for a bone marrow or stem cell transplantation.

How chemotherapy affects your immune system depends on a number of factors

It’s important to note that how exactly chemotherapy affects your immune system can depend on a variety of factors, such as:

  • the type of chemotherapy drug that’s used
  • the dose of chemotherapy that’s used
  • what type and stage of cancer you have
  • your age and overall health

Everyone’s individual situation is different. Be sure to talk with your oncology team about the side effects that you can expect due to chemotherapy.

Many different types of vaccines are in use today. Some are safe for people who’ve had chemotherapy, while others are not. Let’s explore each one in a little more detail now.

Live attenuated vaccines

A live attenuated vaccine contains a live form of a germ that’s been weakened so that it can’t cause disease in healthy people. Some examples of live attenuated vaccines include the:

Because these vaccines contain a live germ, they may cause illness in people with weakened immune systems. This includes people who are currently having or have recently had chemotherapy. Live vaccines are generally not recommended for people who are undergoing or have recently completed chemotherapy.

Inactivated vaccines

Inactivated vaccines contain a whole form of a germ that’s been inactivated or killed. Some examples of inactivated vaccines are the:

Because the germ in these vaccines has been killed, it cannot cause disease in anyone. It’s safe for people who’ve had chemotherapy to receive inactivated vaccines.

Subunit, recombinant, and conjugate vaccines

These vaccines only contain a piece of a germ, typically specific proteins or sugars. Examples of such vaccines are the:

Since these types of vaccines only contain pieces of a germ, they’re also safe for people who’ve had chemotherapy.

Toxoid vaccines

Toxoid vaccines contain toxins from a particular type of bacteria. A toxin is a protein that a bacterium makes that can cause disease.

Examples of toxoid vaccines include those for tetanus and diphtheria. These are both part of the Tdap, DTaP, and Td vaccines.

Toxoid vaccines are also safe for people who have had chemotherapy.

mRNA vaccines

Messenger RNA (mRNA) vaccines work by using an mRNA molecule to teach your own cells to temporarily make a protein from a pathogen. Your immune system can then recognize this protein as foreign and generate an immune response.

As of this article’s publication, the only mRNA vaccines in use are those for COVID-19. These are the Pfizer-BioNTech and Moderna COVID-19 vaccines.

Because mRNA vaccines don’t contain whole, live pathogens, it’s safe for people who’ve had chemotherapy to receive them.

Viral vector vaccines

Viral vector vaccines use a harmless virus that can’t make copies of itself. Once this virus enters cells, the genetic material inside it teaches your cells to make a protein from a pathogen. The immune system can recognize this protein and make an immune response to it.

Similar to mRNA vaccines, the only viral vector vaccine in use is for COVID-19. This is the Johnson and Johnson COVID-19 vaccine.

Viral vector vaccines cannot replicate in the body. As such, they’re safe for people who’ve had chemotherapy.

Live attenuated vaccines aren’t given to people who are currently having or have recently had chemotherapy. However, if you’ll be starting chemotherapy in the future, it may be possible for you to receive these vaccines before starting your treatment.

Other than the flu shot, other vaccines aren’t often given while you’re having chemotherapy. This is because your immune system can become weak during treatment and is less likely to generate an effective immune response.

Your oncologist will also recommend that you wait at least 3 months after your chemotherapy ends before receiving vaccines again. This is to give your immune system time to properly recover from your treatment.

You may be wondering which vaccines are OK to get. Broadly speaking, vaccines that don’t contain live forms of a pathogen are safe for people who’ve recently had chemotherapy.

Vaccine recommendations for people with weakened immune systems

The Centers for Disease Control and Prevention (CDC) recommends the following vaccinations for adults that have a weakened immune system, which can include people who’ve had chemotherapy.

Vaccine Frequency
inactivated or recombinant flu shot once each year
Tdap or Td one dose of Tdap, then a Tdap or Td booster every 10 years
shingles 2 doses at age 19 or older
HPV 3 doses through age 26
pneumococcal 1 dose PCV15 followed by PPSV23 OR 1 dose PCV20
Hib 1 dose
hepatitis B 2, 3, or 4 doses depending on the vaccine
hepatitis A 2 or 3 doses if traveling to an area where hepatitis A is common

It may be possible for some people who’ve had chemotherapy to receive live attenuated vaccines again at some point after their treatment has ended. However, whether this is possible will depend on your level of immune function.

of the three COVID-19 vaccines currently in use in the United States contain live virus. As such, they can safely be given to people who’ve had chemotherapy.

The American Society of Clinical Oncology currently recommends offering COVID-19 vaccines to people who:

  • currently have cancer
  • are undergoing active cancer treatment, including chemotherapy
  • are cancer survivors

All of these groups can safely receive a COVID-19 vaccine, provided that a person has not had any of the following negative responses:

  • a severe allergic reaction after a previous COVID-19 vaccine dose
  • a history of severe allergic reaction to any of the ingredients in a COVID-19 vaccine
  • a known allergy to any of the ingredients in a COVID-19 vaccine
  • a history of a blood clotting condition called thrombosis with thrombocytopenia syndrome after vaccination (Johnson and Johnson vaccine only)

The National Comprehensive Cancer Network (NCCN) recommends that people receiving a stem cell transplant or chimeric antigen receptor (CAR) T-cell therapy should wait at least 3 months after treatment to get vaccinated for COVID-19. According to the National Cancer Institute, CAR T is a newer type of immune therapy that is increasingly being used for lymphoma and other blood cancers such as multiple myeloma.

The NCCN also recommends that people with weakened immune systems get a third shot (not the same as a booster) about 4 weeks after getting their second dose to complete their initial series. Then they should get a booster shot about 3 months after their third shot.

People who have moderately or severely weakened immune systems, including some people who have had chemotherapy, may not make a strong immune response to COVID-19 vaccines. Due to this, the CDC recommends the following vaccine schedule for this group.

Primary vaccine series First doses Additional dose Booster dose
Pfizer-BioNTech 2 doses given 21 days (3 weeks) apart an additional Pfizer-BioNTech dose given at least 28 days (4 weeks) after the second dose a Pfizer-BioNTech or Moderna booster given at least 3 months after the additional dose
Moderna 2 doses given 28 days (4 weeks) apart an additional Moderna dose given at least 28 days (4 weeks) after the second dose a Pfizer-BioNTech or Moderna booster given at least 3 months after the additional dose
Johnson and Johnson 1 dose an additional Pfizer-BioNTech or Moderna dose given at least 28 days (4 weeks) after the first dose a Pfizer-BioNTech or Moderna booster given at least 2 months after the additional dose

People who’ve had chemotherapy can have a weakened immune system that makes them more susceptible to infections. Also, infections can be more serious and harder to clear in this population.

Some of the infections that can cause serious complications in immunocompromised people are preventable by vaccines. A few examples include:

Staying up to date on vaccinations is particularly important when you’ve had chemotherapy. Doing so can help prevent potentially serious illness or complications from vaccine-preventable diseases.

Improving vaccine coverage in people who’ve had chemotherapy is important. For example, a 2020 study surveyed 671 people, most of which were currently having or had recently had chemotherapy. Coverage for the pneumococcal and flu vaccines was found to be only 7.2 and 28.6 percent, respectively.

As with any medication or treatment, vaccines also have side effects. These most often include:

Most vaccine side effects go away on their own within a few days. In the meantime, you can help to ease things like fever and pain by using over-the-counter medications like acetaminophen (Tylenol) or ibuprofen (Advil, Motrin).

Since it’s possible for people who’ve had chemotherapy to have lingering immunosuppression, vaccines may not be as effective as they would be in a healthy individual.

Nevertheless, the benefits from vaccination outweigh the risks. Getting vaccinated can still provide some level of protection against diseases that can cause potentially serious illness.

It’s important to discuss vaccines with your oncology team. They can help to determine the best approach to your individual situation as far as which vaccines you should get and when.

If you’ve had chemotherapy, you’ll need to wait a little bit of time for your immune system to recover. To see if your WBC levels have risen, your oncologist will order a complete blood count (CBC) before vaccination.

This test uses a sample of blood that’s taken from a vein in your arm. It measures the levels of different types of blood cells, including WBCs, and can give your team an idea of your level of immune function.

Vaccines are a vital tool for protecting yourself from certain diseases. While several different types of vaccines are available, not all of them are safe for people who have weakened immune systems, which can happen with chemotherapy.

Vaccines containing a live attenuated form of a pathogen shouldn’t be given to people who are currently having or have recently had chemotherapy. Examples are the MMR vaccine, the chickenpox vaccine, and the flu nasal spray vaccine.

Vaccines made from an inactivated pathogen or that only contain a piece of a pathogen are safe for people who’ve had chemotherapy. This includes the flu shot, the pneumococcal vaccine, and the shingles vaccine.

If you’re currently having chemotherapy or have recently had chemotherapy, ask your oncology team about vaccines. Based on your individual situation, they can let you know which vaccines are recommended and when you can receive them.