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VERIFY: Yes, the COVID-19 Vaccine Can Affect Mammogram Results

Publication: KVUE-TV (ABC, Austin)

AUSTIN, Texas — There's a lot of information out there about vaccines and things you should consider before getting the shot. You may have seen questions about cancer screenings.

A lot of women are asking, can the COVID-19 vaccine affect the results of a mammogram? So we decided to Verify.

Mammograms showing swollen lymph nodes

Physicians at MD Anderson are seeing an uptick of mammograms and other diagnostic imaging exams showing findings that can be confused with cancer in patients who have recently received one of the mRNA COVID-19 vaccines – that's Pfizer or Moderna.

Dr. Julie Sprunt is a breast surgical oncologist with Texas Oncology.

“In the arm where they get a COVID vaccine we’re seeing the lymph nodes and axilla armpit become enlarged after the vaccine – not in every patient that gets the vaccine, but it’s a pretty common reaction,” said Dr. Sprunt.

In clinical trials for the Moderna vaccine, about 16% of patients between 18 and 64 and 8.4% of patients over 65 developed swollen lymph nodes within two to four days after their vaccine.


Lymph nodes are one of your first lines of defense. They typically swell as they react to bacterial or viral infections, and so it is common for vaccines to trigger the same response in your lymph nodes.

“We're noticing that in women who have normal breast imaging, some of the lymph nodes that we can appreciate on mammogram do tend to look a little bit more enlarged following some vaccines. The important thing to know is, in all likelihood, it is a vaccine reaction, and when you go in for breast imaging, it's important to tell the breast imaging team that you've had a recent COVID vaccine and also specifically which arm you had it in,” she said.

Doctors say most people see that reaction on the same side of the body where the vaccine was administered.

“In most people, it takes several weeks up to a couple of months, but most lymph nodes should look normal by that time. However, most of the radiologists are recommending either a follow-up ultrasound, then one to two months to make sure those lymph nodes look okay,” said Dr. Sprunt.

So we can verify: the COVID-19 vaccine can cause a temporary enlargement of lymph nodes. Enlarged lymph nodes can cause a "false positive" on your mammogram.

If you want to get the vaccine, schedule your mammogram before your first dose or wait four to six weeks after your second dose.

Breast cancer survivor tips

Here are some other tips if you are a current or past breast cancer patient. You can ask to receive the vaccine in the arm opposite of the side of your body where you had cancer.

If you have cancer in your right breast, for instance, get the vaccine in your left arm. And, if you have cancer in your left breast, get vaccinated in your right arm.

For women who have cancer in both breasts, talk to your doctor. You can get the COVID-19 vaccine shot administered in your leg. Dr. Sprunt said it can be more uncomfortable to get it in your thigh, but it is a possibility.

Enlarged lymph nodes can falsely affect cancer screening and diagnostic imaging results up to six weeks after vaccination.

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