Getting an updated COVID-19 booster vaccine is an important part of healthy living as a breast cancer survivor. Over the past few years of the pandemic, you may have heard that the COVID-19 vaccine can affect your mammogram results. Specifically, it can cause lymphadenopathy (lymph node swelling) that may show up on your breast cancer screening tests.

In this article, we’ll discuss what to know about the COVID-19 vaccine and scheduling your regular mammograms. There’s no evidence that links the COVID-19 vaccine to breast cancer. In fact, vaccination may be even more important for people who survive cancer, as they’re at a higher risk of developing severe illness from COVID-19 compared to the general population.

The U.S. Food and Drug Administration (FDA) has authorized updated COVID-19 booster vaccines for the fall of 2023. If you’re due for your annual breast cancer screening too, make sure to let your doctor’s office know if you’ve recently gotten your booster.

The New Monovalent COVID-19 Vaccines

The FDA approved the new round of updated messenger RNA (mRNA) COVID-19 vaccines for adults and children ages 6 months and up. These new versions of the Moderna and Pfizer vaccines are recommended by the Centers for Disease Control and Prevention (CDC).

The previous round of mRNA vaccines were bivalent, meaning they contained blueprints of spike proteins found in two different versions of SARS-CoV-2, the virus that causes COVID-19. These new vaccines are monovalent — they contain the blueprints of a single variant, called Omicron variant XBB.1.5 and nicknamed “Kraken.”

Health experts have identified XBB.1.5 as being highly transmissible and contagious. People who’ve received previous vaccinations or previously had COVID-19 have still been infected with this newer variant.

Who Should Get the New Vaccine?

All people ages 5 and up are eligible for one dose of the new vaccine as long as it’s been at least two months since their last vaccination. Children 6 months to 4 years old may receive more than one dose of the new vaccine, depending on their vaccination status.

People who are moderately or severely immunocompromised (have weakened immune systems) also should receive the new vaccine. The CDC cautions that these people are “at increased risk of severe COVID-19 illness and death.”

Are the New Vaccines Safe?

The FDA based its approval of the new mRNA vaccines on the safety and effectiveness of previous versions, which were manufactured in the same way as the new round. Per the CDC, millions of Americans have received COVID-19 vaccines “under the most intense safety monitoring program in U.S. history.”

The FDA noted that the benefits of receiving the vaccine outweigh any risks. Potential side effects — both common and rare but serious — are similar to those of previous versions of the vaccine. Common side effects are generally similar to flu symptoms, including temporary fever, chills, aches, and fatigue, along with irritation or soreness at the injection site.

COVID-19 Vaccines Can Cause Lymph Node Swelling

Vaccines teach your immune system how to recognize and fight invading viruses. When your immune system sees a protein or antigen from the COVID-19 vaccine, it creates an immune response. Your body makes more white blood cells (WBCs) to fight the infection.

Your lymphatic system is an important part of keeping you healthy. It helps balance your body’s fluid levels and filter out viruses and bacteria. During an infection, your WBCs can collect in your lymph nodes. This leads to fluid buildup and swelling. If you’ve ever gone to the doctor’s office when you’re sick, your health care provider may have felt for swollen lymph nodes in your neck.

It’s a good sign if you have enlarged lymph nodes after a vaccination — this means your immune system is working hard to build immunity. It’s also important to know that the COVID-19 vaccine isn’t the only vaccine that causes lymphadenopathy. According to doctors at MD Anderson Cancer Center, the vaccines for influenza (the flu) and human papillomavirus (HPV) may also cause swelling.

Lymphadenopathy Can Affect Breast Cancer Screenings

The lymph nodes in your armpits — known as your axillary lymph nodes — can also swell with infection or after a vaccination. The term “axillary lymph nodes” may sound familiar to breast cancer survivors. Many people have their axillary lymph nodes checked and removed during their breast cancer diagnosis to make sure their cancer hasn’t spread.

On your mammogram, a radiologist or imaging specialist will look for masses and other signs of breast cancer. If they find lymph node swelling in addition to other signs of cancer, they’ll likely order additional tests to confirm a cancer diagnosis. Axillary adenopathy (swelling in your axillary lymph nodes) may be a sign that breast cancer is growing or has returned.

One of the side effects of COVID-19 vaccines is temporary swelling of your lymph nodes in your armpit. If you’ve recently had your COVID-19 vaccine around the time of your mammogram, it may complicate the results. A 2023 study notes that axillary lymph node swelling is seen in up to 44 percent of mammograms after COVID-19 vaccination. This means your doctor and radiologist may have a harder time telling whether the swelling is from your vaccine or potentially cancer.

An MRI scan is another tool used to screen for and diagnose breast cancer. MRI scans are typically used to screen people who are at a high risk of developing breast cancer at some point in their lives. One study from the journal Clinical Imaging using MRI scans found that only 7.7 percent of women who had a COVID-19 vaccine within the past year had swelling in their axillary lymph nodes.

The study authors also noted that of women with swollen axillary lymph nodes, only 3.3 percent had cancer. They found that all of the women had other suspicious signs of breast cancer. This means that even if you have swollen lymph nodes on your breast cancer screening, there are usually other signs your doctor or radiologist can see to help them make a diagnosis.

Should You Change Your Breast Cancer Screening Around Your COVID-19 Vaccine?

Recent studies show that you shouldn’t change your mammogram around your COVID-19 vaccine. In 2021, the Society of Breast Imaging originally released a statement saying that mammograms should be delayed for four to six weeks after a COVID-19 vaccination. However, with new information available in 2023, this recommendation is outdated and has been removed.

Now, the Society of Breast Imaging states that you shouldn’t delay your mammogram around a COVID-19 vaccine. This is because researchers found that lymph node swelling can last as long as 43 weeks after a COVID-19 vaccination. It’s important not to delay your mammogram or MRI scans and keep up with your breast cancer care. Even if your doctor or radiologist does find some lymph node swelling, they can follow up with monitoring and additional scans.

When you go in for your scans, let your health care provider know when your last COVID-19 vaccination was and what arm you received it in. If they notice any axillary lymph node swelling near the arm you were vaccinated in, they may run additional tests.

Talk With Your Doctor

If you have more questions about the COVID-19 booster vaccine and timing your mammogram, talk to your doctor. They’ll make recommendations that best fit your breast cancer care plan while keeping you protected from COVID-19.

If you have an upcoming mammogram and need to get a booster vaccination, consider getting the shot on the opposite side your cancer was on. For example, if you previously had cancer in your left breast, it’s a good idea to get your COVID-19 vaccine in your right arm. If you’ve had breast cancer in both breasts, your doctor may recommend one arm over the other based on your previous treatments.

Find Your Team

MyBCTeam is the social network for people with breast cancer and their loved ones. On MyBCTeam, more than 65,000 members come together to ask questions, give advice, and share their stories with others who understand life with breast cancer.

Have you received your COVID-19 vaccine or updated booster around the time of your mammogram? How did it affect your experience or results? Share your story in the comments below, or start a conversation by posting on your Activities page.