Join Us

COVID-19 Vaccine Facts for People With Breast Cancer

Save as Favorite
Sign in to receive recommendations (Learn more)

In December 2020, the U.S. Food and Drug Administration (FDA) authorized the first COVID-19 vaccines for emergency use: the Pfizer-BioNTech COVID-19 vaccine and the Moderna COVID-19 vaccine. The Johnson & Johnson (J&J) COVID-19 vaccine (also called the Janssen vaccine) was authorized in February 2021. Other COVID-19 vaccines are being used in other countries, and others are being developed and may eventually be approved, as well.

Because the vaccines do not contain live viruses, they can be used in people with weakened immune systems, including people being treated for cancer. The FDA has found that these vaccines are safe and highly effective for preventing COVID-19, especially serious illness and death from the disease. It is still unclear how long the protection lasts and whether you can give someone else COVID-19 if you are exposed to the virus after being vaccinated. So it's recommended that mask wearing and physical distancing in public continue for some time.

Experts have recommended that most people with cancer or a history of cancer should get a COVID-19 vaccine. Still, you should talk to your doctor about whether getting vaccinated is the right decision for your individual situation.

Research has shown that people with cancer seem to have much less protection after the first Pfizer vaccine injection compared to people without cancer. But after the second shot — given early, after 3 weeks instead of 4 weeks, in the study — people with cancer had suitable protection. This result emphasizes the importance of getting the second injection of a vaccine on time. Podcast logo

Update on COVID-19 Vaccines
with Halle Moore, M.D.
Listen to the episode to learn how the vaccines are different, how Dr. Moore is advising people with certain allergies about the vaccines, and what people currently being treated for breast cancer need to know before being vaccinated.

About 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 coronavirus’s mRNA, and that 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. So, if you’re ever exposed to the COVID-19 virus, your immune system is ready to recognize the virus and protect you from infection.

Because mRNA is just a small piece of the virus copied in a lab, the vaccine cannot cause COVID-19, and it is considered safe for people with weakened immune systems. However, it is unclear whether the vaccine may be less effective and offer less protection against COVID-19 in people with weakened immune systems.

The Pfizer-BioNTech vaccine can be used in people age 12 and older, and the Moderna vaccine can be used in people age 18 and older. Both mRNA vaccines are given as two separate injections in the upper arm muscle. The Pfizer-BioNTech vaccine consists of two doses given 3 weeks apart, and the Moderna vaccine consists of two doses given 1 month apart. You will be most protected against COVID-19 about 2 weeks after your second shot.

People who have received two doses of either mRNA vaccine — Pfizer or Moderna — are up to 91% less likely to develop COVID-19 compared to people who are unvaccinated, according to results from the RECOVER study published online on June 30, 2021, by the New England Journal of Medicine.1

The same study also found that people who were partially vaccinated with either mRNA vaccine were 81% less likely to develop COVID. In this study, partially vaccinated meant either:

  • it was 14 days or more after a person had the first dose of an mRNA vaccine and had not received the second dose yet
  • it was less than 14 days after the second dose of an mRNA vaccine

Among the 3,975 people in the study, 16 fully- or partially-vaccinated people developed COVID. These people with “breakthrough” cases had less severe symptoms and were sick for a shorter amount of time than average.

The RECOVER study is ongoing and future results will help doctors figure out how long COVID-19 vaccines protect against infection. Podcast logo

Understanding the COVID-19 Vaccines
with Hana El Sahly, M.D.
Listen to the episode to learn how the mRNA vaccines work, the differences between the two, and the safety and effectiveness of the vaccines in people with weakened immune systems.

Back to top

About the Johnson & Johnson vaccine

The J&J COVID-19 vaccine works differently than the mRNA vaccines. The J&J vaccine is called a viral vector vaccine. It is made from an adenovirus (the type of virus that causes the common cold). The adenovirus in this vaccine is not a live virus — it has been changed in a lab so that it can't reproduce in the body or cause disease. Also, a gene found in the COVID-19 virus has been added to this modified adenovirus. This gene tells your body to make copies of the COVID-19 virus's spike protein. Then your immune system gets activated and builds up immune cells and antibodies to fight the spike protein. Once this happens, your immune system is ready to protect you if you are exposed to the COVID-19 virus.

The J&J vaccine can be used in people age 18 and older. It is given as a single injection in the upper arm muscle. You are considered fully vaccinated 2 weeks after you get the single shot of this vaccine.

Rare but serious side effects linked to the J&J vaccine

On July 12, 2021, the FDA warned that the J&J vaccine may lead to a higher risk of Guillain-Barré syndrome in the 6 weeks after vaccination in a small number of people.

A warning about Guillain-Barré syndrome has been added to the J&J fact sheets and the CDC website.

It’s important to know that this side effect is rare and only a small number of people have developed Guillain-Barré syndrome. As of July 13, 2021, about 12.5 million people in the United States received the J&J vaccine and about 100 people have developed Guillain-Barré syndrome.

According to the CDC, the cases of Guillain-Barré syndrome were mostly reported about 2 weeks after a person was vaccinated and mostly in men aged 50 and older.

"Although the available evidence suggests an association between the [J&J] vaccine and increased risk of [Guillain-Barré syndrome], it is insufficient to establish a causal relationship," the FDA said in a statement. "Importantly, the FDA has evaluated the available information for the Janssen COVID-19 vaccine and continues to find the known and potential benefits clearly outweigh the known and potential risks."

Guillain-Barré syndrome is a rare disorder of the nervous system. In Guillain-Barré syndrome, the body’s immune system attacks the peripheral nervous system, the network of nerves outside the brain and spinal cord. Symptoms range from brief muscle weakness in mild cases to paralysis in severe cases. Doctors don’t know the exact cause of Guillain-Barré syndrome, but do know that it is not contagious or inherited.

You should seek medical attention right away if you develop any of the symptoms below after receiving the J&J vaccine:

  • weakness or tingling feelings, especially in the arms or legs, that gets worse and spreads to other parts of your body
  • difficulty walking
  • difficulty using facial muscles, including speaking, chewing, or swallowing
  • double vision or inability to move your eyes
  • difficulty controlling your bladder or bowels

On April 13, 2021, the FDA and CDC recommended that use of the J&J vaccine be paused after six women who received the vaccine developed a rare blood clotting disorder about 9 days after being vaccinated. As of April 21, there were 15 cases and three people died. On April 23, after reviewing the data, the CDC lifted the pause and again recommended the use of the J&J vaccine for all adults.

A warning about the rare clotting disorder has been added to the J&J vaccine fact sheets and the CDC website. Podcast logo

J&J COVID Vaccine and Blood Clots: What This Means for People With Breast Cancer
with Brian Wojciechowski, M.D.
Listen to the episode to learn about the blood clots and how they happen, what people who have received the J&J vaccine should know, and what people with breast cancer should know about the vaccine.

It’s important to know that the clotting disorder, which is being called vaccine-induced immune thrombotic thrombocytopenia, abbreviated VITT, is rare.

“What I know about conditions like this, such as [a very similar condition caused by the blood thinner heparin called HITT], is that they’re very rare. I don’t want to say it’s extremely rare," explained Brian Wojciechowski, M.D., a medical oncologist and medical adviser. "I think we need to look at it more. I think the FDA needs to investigate any other cases that may have come up. But it should be fairly uncommon.”

A thrombosis is a blood clot. In most cases reported after the J&J vaccine, the clot was in the veins that drain blood from the brain. This is why you may have seen the disorder called cerebral venous sinus thrombosis (CVST). The blood clots also can form in the legs, abdomen, or heart and can cause a stroke.

All of the patients had thrombocytopenia. Thrombocytopenia means a person has very low levels of platelets, a type of cell that helps the blood to clot. More research is needed, but it is thought that the J&J vaccine may trigger an immune system response that is destroying platelets but also causing the platelets to release tiny particles that lead to blood clots forming.

Symptoms of these rare clots include:

  • severe headache
  • severe abdominal pain
  • severe leg pain or redness, especially in only one leg
  • shortness of breath or chest pain

Because these rare clots are seen in people with very low platelet counts, they can’t be treated with heparin, the most commonly used blood thinning medicine.

The FDA and CDC said they called for the pause on using the J&J vaccine out of an abundance of caution. The goal of the pause was to give doctors and other healthcare providers the time to learn how to diagnose and treat the clotting disorder.

"The issue with these types of blood clots is if one administered standard treatment, one can actually cause tremendous harm or the outcome can be fatal," Dr. Peter Marks, director of the FDA Center for Biologics Evaluation and Research, said at a media briefing.

So, the FDA and the CDC paused use of the J&J vaccine to be sure doctors knew about the clotting condition and how to properly treat it.

If you have an upcoming appointment to get the J&J vaccine, you should talk to your doctor about whether the J&J vaccine is safe for you.

If you received the J&J vaccine 30 or more days ago, your risk of developing the rare clotting disorder is very low. There are no known cases that started 3 weeks after receiving the vaccine.

If you received the J&J vaccine in the past few days, the flu-like symptoms that you may have are normal. But if you have any of these symptoms:

  • severe headache
  • severe abdominal pain
  • severe leg pain or redness, especially in only one leg
  • shortness of breath or chest pain

you should contact your doctor or seek medical care immediately and explain that you’ve had the J&J vaccine, as well as the date you received it.

Back to top

COVID-19 vaccine side effects

The most common side effects of the COVID-19 vaccines have been:

  • pain or soreness in the arm where you receive the injection
  • tiredness
  • headache
  • muscle or joint pain
  • chills
  • fever

These side effects are usually minor, last a few days, and happen more often after the second dose. 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. Doctors call this “axillary adenopathy.”

If you have had 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 the COVID-19 vaccines. To lower this risk, people with a history of breast cancer should ask to have the vaccine injection in the arm on the opposite side of the body where the breast cancer was. If you have had breast cancer in both breasts, talk with your doctor to decide which arm you should choose for the injection. The COVID-19 vaccines can be given in the upper hip area as an alternative, but the providers at your vaccination site may not be trained or comfortable with giving the vaccine this way, so this may not be a feasible option for most people at this time.

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 a cancer but it turns out to be normal. A false positive mammogram result can lead to unnecessary stress and additional testing.

The Society of Breast Imaging has recommended that women should try to schedule their routine screening mammogram at least a month after getting vaccinated so that any swelling in the axillary lymph nodes has time to go away. But if your mammogram is already scheduled, it is not necessary to cancel your mammogram or your COVID-19 vaccine appointment. Just be sure to tell the person performing your mammogram if you were recently vaccinated, in which arm, and whether it was your first or second dose. This will help the breast radiologist accurately interpret your mammogram result.

People are monitored for about 15 to 30 minutes after receiving each injection 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-19 vaccine is safe for you.

The person who gives you the COVID-19 vaccine should ask if you have had any severe allergic reactions in the past. Make sure you tell them if you have experienced an allergic reaction so they monitor you for at least 30 minutes after you receive your injection. Vaccination centers should have medicines, equipment, and safety measures in place to care for anyone who has an allergic reaction. It’s a good idea to ask if these safety measures are in place at your vaccination center if you have had a serious allergic reaction in the past.

It's important to know if you have 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-19 vaccines.

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

The CDC has said that if you have had a severe allergic reaction to PEG in the past, then you should not get the Pfizer or Moderna mRNA vaccines and should ask your doctor about getting the J&J vaccine instead. If you have had a severe allergic reaction to polysorbate in the past, then you should not get the J&J vaccine and should ask your doctor about getting one of the mRNA vaccines instead.

Medicines that contain PEG are called “pegylated” by doctors. 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), a chemotherapy medicine used to treat breast cancer. Also marketed as Caelyx in some countries.
  • Neulasta (chemical name: pegfilgrastim), a medicine used to treat neutropenia (low white blood cell levels) during chemotherapy.

Polysorbate is used in many medicines to change how they work in the body or as a preservative. Cancer medicines that contain polysorbate include:

  • Abraxane (chemical name: albumin-bound or nab-paclitaxel)
  • Adriamycin (chemical name: doxorubicin)
  • Aranesp (chemical name: darbepoetin alfa)
  • Cinvanti, Emend (chemical name: aprepitant)
  • Doxil (chemical name: pegylated liposomal doxorubicin); also marketed as Caelyx in some countries
  • Epogen (chemical name: epoetin alfa)
  • Methotrexate (marketed with many brand names)
  • Procrit (chemical name: epoetin alfa)
  • Taxol (chemical name: paclitaxel)
  • 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.

Back to top

When you’re fully vaccinated

As more people have been vaccinated against COVID-19, the CDC continues to update its guidelines on what fully vaccinated people can do. These guidelines also take into account how contagious the current strains of COVID-19 are.

On July 27, 2021, the CDC recommended that fully vaccinated people should wear masks in indoor public settings if they live in areas where COVID-19 is spreading at “substantial” or “high” levels. This CDC tool will show you whether COVID-19 is spreading at low, moderate, substantial, or high levels where you live.

All unvaccinated people should wear a mask in public indoor and outdoor settings.

These extra precautions are being recommended because a newer strain of COVID-19, called the Delta variant, is more contagious than previous strains and is spreading throughout the United States. Getting sick from COVID-19 — even the Delta variant — seems to be rare in people who are fully vaccinated, but it can happen. Still, “breakthrough infections” in people who are fully vaccinated almost never cause severe illness or hospitalization.

The CDC says that fully vaccinated people have a lower risk of transmitting COVID-19 to people who are unvaccinated. But it’s unclear if fully vaccinated people can spread the Delta variant more easily than other strains of COVID-19.

The latest CDC recommendations also say that everyone should wear masks in schools. The CDC also says that all fully vaccinated people might want to wear a mask in public indoor settings for extra protection, especially if they have a weakened immune system or live with someone who has a weakened immune system or a higher risk of severe illness from COVID-19. If you’re immunocompromised, the CDC recommends that you talk to your doctor about taking extra precautions, even if you are fully vaccinated. If you know someone who is immunocompromised or has a medical condition, such as cancer, that puts them at higher risk for severe complications from COVID-19, it’s a good idea to wear a mask when you visit them indoors, even you both are fully vaccinated.

Certain breast cancer treatments, including chemotherapy, targeted therapy, and immunotherapy, can weaken the immune system. The COVID-19 vaccines may offer less protection in people who are receiving cancer treatment, so you may need to continue taking extra precautions.

People are considered fully vaccinated:

  • 2 weeks after their second dose of the Pfizer or Moderna vaccine
  • 2 weeks after the single dose of the Johnson & Johnson vaccine

If you’re fully vaccinated, CDC recommendations say you:

  • can gather indoors without a mask or physical distancing, except in places where masks are required (such as schools, businesses, hospitals, correctional facilities, homeless shelters, and public transportation), or in areas where COVID-19 cases are spiking
  • can take part in outdoor activities and recreation without a mask, even in crowded settings and venues
  • travel within the United States without a COVID test before or after travel
  • travel internationally without a test before travelling, and without quarantining after travel, depending on your destination

It’s important to know that international travelers coming to the United States are still required to show a negative COVID test result or documentation of recovery from COVID-19 before boarding a flight to the United States.

Even if you’re fully vaccinated, the CDC still recommends you:

  • wear a mask in public indoor settings if you live in an area where COVID-19 cases are spiking
  • get tested if you are around someone you suspect has COVID-19, and wear a mask in public indoor settings for 2 weeks or until you get a negative test result
  • talk to your doctor about whether you need to continue to wear a mask and take other precautions if you or someone you live with is receiving medical treatments that can weaken the immune system, or is at risk for severe illness from COVID-19
  • wear a mask that fits snugly where required by law or other rules and regulations
  • wear a mask when you travel on planes, buses, trains, and other types of public transportation
  • wash your hands with soap and water for at least 20 seconds or use hand sanitizer after you’ve been in public spaces
  • watch out for symptoms of COVID-19, especially if you’ve been around someone who is sick
  • get tested and quarantine if you develop symptoms

Back to top

Written by:

Adam Leitenberger, editorial director

Jamie DePolo, senior editor

This content was developed with contributions from the following experts:

Halle Moore, M.D., director of breast oncology, Cleveland Clinic

Marisa Weiss, M.D., chief medical officer

Brian S. Wojciechowski, M.D., medical adviser


  1. Thompson MG, et al. “Prevention and Attenuation of Covid-19 with the BNT162b2 and mRNA-1273 Vaccines.” New England Journal of Medicine. June 30, 2021. Available at:

Was this article helpful? Yes / No
Rn icon

Can we help guide you?

Create a profile for better recommendations

How does this work? Learn more
Are these recommendations helpful? Take a quick survey

2021eg sidebarad v01
Back to Top