COVID-19 Vaccines and Breast Cancer: What You Need To Know

Experts recommend that all people ages 6 months and older get a COVID vaccine. They also recommend that most people with cancer or a history of cancer get an updated COVID vaccine. If you have cancer or a history of cancer, it’s a good idea to talk with your doctor about whether getting the latest COVID vaccine is the right decision for your individual situation.

There’s no link between the COVID vaccines and breast cancer risk or developing breast cancer.

The U.S. Centers for Disease Control and Prevention (CDC) says that everyone ages 6 months and older should get the 2024–2025 COVID-19 vaccine. This includes people who have already received a COVID vaccine and those who have had COVID.

There are three choices of 2024–2025 COVID vaccines for people ages 12 and older:

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  Pfizer-BioNTech vaccine: one shot, even if it’s your first time getting a COVID vaccine. 

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  Moderna vaccine: one shot, even if it’s your first COVID vaccine. 

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  Novavax vaccine: one shot if you’ve received a COVID vaccine in the past; two shots, three weeks apart, if it’s your first COVID vaccine. 

If you have a weakened immune system, called immunocompromised by doctors, you may get additional doses of the 2024–2025 updated Pfizer-BioNTech, Moderna, or Novavax COVID-19 vaccine. This is because people with moderately to severely compromised immune systems are especially vulnerable to COVID, and may not build the same level of immunity to the virus as people who are not immunocompromised after being fully vaccinated.

Many breast cancer treatments, including chemotherapy, certain targeted therapies, and immunotherapy, can weaken your immune system. Still, it's important to know that not everyone with a history of breast cancer is immunocompromised. It depends on the treatments you received and how long ago you received them, as well as any other health conditions you have.

If you’re an adult and are currently receiving treatment for breast cancer or have received breast cancer treatment in the past, it’s a good idea to ask your doctor if you should follow the CDC recommendations for moderately to severely immunocompromised people.

If you’re immunocompromised, you may want to ask your doctor about the antibody therapy Pemgarda (chemical name: pemivibart). It’s used to prevent COVID in people ages 12 and older who have moderately to severely compromised immune systems, but can only be used when 90% or more of the COVID variants that are infecting people would respond to Pemgarda.

Pemgarda is given as a single intravenous infusion. Pemgarda can only be used to prevent COVID-19 before you’re exposed to the virus. It can’t be used after you’ve been exposed to COVID-19 or if you’re currently infected with COVID-19.

The most common side effects of Pemgarda are infusion site reactions, headache, fatigue, and nausea.

The most commonly reported side effects of the COVID vaccines are:

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  pain or soreness in the arm where you receive the injection

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  tiredness

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  headache

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  muscle or joint pain

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  chills

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  fever

These side effects are usually minor and last a few days. Side effects are expected and are actually a sign that the vaccine is working by causing an immune response. Research shows that women may experience worse side effects from the COVID vaccines than men.

Some people have experienced swollen or enlarged lymph nodes, including the axillary lymph nodes (the lymph nodes in the armpit) on the side where the injection was given. Doctors call this “axillary adenopathy.”

The side effects of all three COVID vaccines are similar, though some studies and anecdotal evidence suggest that the Novavax vaccine may cause fewer side effects. Still, those studies were done on the 2023-24 versions of the vaccines, not the most recent 2024-25 versions. It’s unclear that will be the case in 2025. Also, no studies have compared the vaccines head to head.

There’s no evidence linking COVID-19 vaccines to cancer. Both the U.S. National Cancer Institute and the American Cancer Society report there’s no information that COVID-19 vaccines cause cancer. There’s also no evidence that suggests the vaccine can make cancer grow or come back (recur).

If you’ve received treatment for breast cancer, and especially if you’ve had underarm lymph nodes removed, you could experience lymphedema or worsening of lymphedema as a side effect of a COVID vaccine. To lower this risk, people with a history of breast cancer should avoid getting the vaccine injected into the arm on the side of the body where they had breast cancer. If you have a history of breast cancer in both breasts, ask your doctor which arm should be injected. If the breast cancers were diagnosed at different times, doctors usually recommend giving the vaccine in the arm on the side that was diagnosed first, or the side that had the least extensive underarm surgery.

The COVID vaccines can be given in the upper hip area as an alternative, but some providers may not be trained in or comfortable with giving the vaccine this way, so this may not be a feasible option.

People are monitored for about 15 to 30 minutes after receiving a vaccine to make sure they don’t have a rare serious allergic reaction to the vaccine. If you have a history of severe allergic reactions, you should talk with your doctor and perhaps see an allergist or immunologist to figure out whether getting a COVID vaccine is safe for you.

The person who gives you the COVID vaccine should ask if you’ve had any severe allergic reactions in the past. Make sure you tell them if you’ve experienced an allergic reaction so they monitor you for at least 30 minutes after you receive your injection. You may also want to ask them about safety measures in place should you have an allergic reaction.

It’s important to know if you’ve ever had an allergic reaction to polyethylene glycol (PEG) or polysorbate in the past. These ingredients are in certain medicines, including some cancer therapies, and are also used in the COVID vaccines, as well as Pemgarda.

The Pfizer and Moderna vaccines contain PEG. They do not contain polysorbate, but polysorbate is closely related to PEG.

The CDC has said that if you've had a severe allergic reaction to PEG in the past, then you should not get the Pfizer or Moderna vaccine.

Doctors call medicines that contain PEG “pegylated.” Medicines are sometimes pegylated to change how they work in the body. Sometimes there are pegylated and non-pegylated versions of the same medicine.

Pegylated cancer medicines include Doxil (chemical name: pegylated liposomal doxorubicin), and Neulasta (chemical name: pegfilgrastim).

Polysorbate is used in many medicines to change how they work in the body or as a preservative. Certain chemotherapy medicines contain polysorbate including, Abraxane (chemical name: albumin-bound or nab-paclitaxel), Adriamycin (chemical name: doxorubicin), Taxol (chemical name: paclitaxel), and Taxotere (chemical name: docetaxel).

If you have had a severe allergic reaction to any of these medicines, talk to your doctor about whether getting a COVID-19 vaccine is safe for you.

For people without a history of breast cancer, swelling of the axillary lymph nodes after vaccination is harmless, but they can feel like breast lumps and cause some women to worry they could be a sign of breast cancer. These swollen lymph nodes can also show up on a mammogram, even if you can’t feel them. This could result in a false positive, which is when a mammogram shows an abnormal area that looks like cancer but turns out to be normal. A false positive mammogram result can lead to unnecessary stress and additional testing.

While some organizations and doctors previously recommended that women wait four to six weeks after receiving a COVID-19 vaccine to get a mammogram, the Society of Breast Imaging now says that you don’t need to wait to get a mammogram. Just be sure to tell the person doing the mammogram that you were recently vaccinated and in which arm. This helps the breast radiologist accurately interpret your mammogram result.

The Pfizer-BioNtech and Moderna vaccines work by using genetic material called messenger RNA (mRNA). The mRNA vaccines contain a small piece of the coronavirus’s mRNA, which tells your body to make copies of a protein in the virus called the spike protein. Your immune system then builds up immune cells and special proteins (antibodies) to fight the spike protein.

The Novavax vaccine uses traditional vaccine technology, which has been used in vaccines to prevent shingles, diphtheria, tetanus, and whooping cough. It is a subunit vaccine.

Instead of telling your body to make copies of the spike protein like the mRNA vaccines do, the Novavax vaccine contains pieces of the spike protein, which then trigger your body to mount an immune response. The spike protein is created in a lab and is inactivated so it can’t make you sick. The vaccine also contains another ingredient called an adjuvant that helps create a stronger immune response.

In May 2023, the CDC announced that the J&J vaccine was no longer approved or available in the United States and that any remaining doses of the J&J vaccine should be discarded.