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

As in past years, people with a history of breast cancer are advised to get this year’s vaccine. The U.S. Food and Drug Administration (FDA) approved four updated COVID-19 vaccines in August 2026: two from Moderna (Spikevax and mNexspike), the Pfizer-BioNTech Comirnaty vaccine, and the Sanofi Nuvaxovid vaccine.

There’s no link between the COVID-19 vaccines and breast cancer risk or developing breast cancer.

The Moderna Spikevax vaccine is approved for people ages 6 months to 64 years with at least one underlying health condition that puts them at high risk for severe outcomes from COVID-19, and all people age 65 and older.

The Moderna mNexspike vaccine has a more targeted design than the Spikevax vaccine, so contains one-fifth the mRNA dose compared to Spikevax. It’s approved for people ages 12 through 64 who have at least one underlying health condition that puts them at high risk for severe COVID-19, and all people age 65 and older.

The Pfizer-BioNTech Comirnaty vaccine is approved for all people ages 65 and older, as well for people ages 5 through 64 with at least one underlying health condition that puts them at high risk for severe outcomes from COVID-19.

The Sanofi Nuvaxovid vaccine (commonly called Novavax) is the only non-mRNA vaccine option. It’s approved for people ages 65 and older, as well as people ages 12 to 64 who have at least one underlying health condition that puts them at high risk for severe COVID-19 outcomes.

Besides a history of cancer, underlying health conditions that put you at high risk for severe COVID-19 outcomes include a history of stroke, heart disease, diabetes, and a number of lung diseases.

People younger than 65 who don’t have one of the specified health conditions may still be able to get a vaccine, but it’s unclear if they can be vaccinated at a pharmacy or have to go to a doctor’s office. It’s also not clear if all insurance plans will cover the shots for these people.

In September 2025, the CDC’s vaccine advisory committee stopped recommending COVID-19 vaccines for specific groups of people. Instead, it has said that people should be told about the risks and benefits of a COVID-19 vaccine and make a decision based on their own personal risk.

Many doctors and experts disagree with the limits because they feel many people would benefit from the vaccines. The American Academy of Family Physicians (AAFP), the American Academy of Pediatrics (AAP), the American College of Obstetricians and Gynecologists (ACOG), and the Infectious Diseases Society of America (IDSA) issued their own vaccine recommendations for the 2026 fall respiratory virus season. They recommend that all adults get an updated COVID-19 vaccine. They also recommend that women who are pregnant or breastfeeding should get an updated COVID-19 vaccine.

If you have breast cancer or a history of breast cancer, it’s a good idea to talk with your doctor about whether getting a new COVID-19 vaccine makes sense for you.

Precautions other than a vaccine for people with weakened immune systems

Many breast cancer treatments, including chemotherapy, certain targeted therapies, and immunotherapy, can weaken your immune system. If you have a weakened immune system, called immunocompromised by doctors,  you may want to ask your doctor about the antibody therapy Pemgarda (chemical name: pemivibart).

Pemgarda is given as a single intravenous infusion. It’s used to prevent COVID-19 in people age 12 and older who have moderately to severely compromised immune systems, but can only be used when 90% or more of the COVID-19 variants that are infecting people would respond to Pemgarda. The most common side effects of Pemgarda include infusion site reactions, headache, fatigue, and nausea.

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 commonly reported side effects of the COVID-19 vaccines are pain or soreness in the arm where you receive the injection, tiredness, headache, muscle or joint pain, chills, and 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-19 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.

The side effects of all four COVID-19 vaccines are similar, though some studies and anecdotal evidence suggest that the Novavax vaccine may cause fewer side effects. Still, 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.

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.

Ingredients to watch for

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 mRNA COVID vaccines, as well as Pemgarda.

The Pfizer and Moderna vaccines contain PEG. The Sanofi Novavax vaccine contains polysorbate. 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.

If you’re scheduled for a mammogram within four to six weeks of getting a COVID-19 vaccine, 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 mRNA vaccines: Pfizer and Moderna

The Pfizer-BioNtech and Moderna vaccines work by using genetic material called messenger RNA (mRNA). The mRNA vaccines contain a small piece of the virus’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

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

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.