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Provider prepares woman for a breast exam
Provider prepares woman for a breast exam
Provider prepares woman for a breast exam

COVID-19 Vaccine: Can It Affect Your Mammogram Results?

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Getting vaccinated for COVID-19 is an important way to protect yourself from potentially serious effects of the coronavirus. Likewise, getting regular mammograms as your doctor recommends can keep you safer by catching breast cancers early, when they might be easier to treat.

There is no connection between the COVID-19 vaccine and breast cancer. But what should women know about how the COVID-19 shots might affect the results of their mammograms? Lisa Mullen, M.D., a radiologist who specializes in breast imaging, offers some perspective and answers your questions.

Getting the COVID-19 vaccine can cause temporary lymph node enlargement and result in a “false positive” mammogram.

The COVID-19 vaccine, like other vaccinations, can cause a temporary enlargement of lymph nodes. This can cause your mammogram to appear abnormal even when you are OK and there is no indication of cancer.

But, enlarged lymph nodes can result in a “false positive” on your mammogram. You may get a request to return for further testing — a call-back — which can be unsettling.

The COVID-19 Vaccine and Enlarged Lymph Nodes

How do vaccines such as the COVID-19 vaccine affect lymph nodes?

Mullen says, “Lymph nodes under the arm where a person has gotten a vaccine can become enlarged as part of the normal immune response to the vaccine.”

Not all vaccines cause swollen lymph nodes, but ones that cause a more intense immune response, such as the COVID-19 vaccine, some shingles vaccines, and others, are more likely to affect them. “The COVID-19 vaccine is a new type of vaccine, and people are reacting strongly to it,” Mullen says. “That heightened immune response is normal and expected.”

For people getting a two-part coronavirus vaccine (such as the Moderna or Pfizer type), is lymph node enlargement more likely after the second shot?

Mullen says that larger lymph nodes can appear after the first or second vaccination.

Is COVID-19 vaccine lymph node enlargement permanent?

No, Mullen says. Your lymph nodes will return to normal size a few weeks after your vaccination regimen is complete.

Can other vaccines cause lymph node changes on a mammogram?

Yes. Mullen says, “Other vaccines that activate the immune system can change the appearance of your lymph nodes, such as the shingles shot, the pneumonia shot or the diphtheria/tetanus/pertussis (D-TaP) shot. Getting more than one vaccination at a time can cause a more prominent immune response, such as if you get a flu shot at or near the same time as an additional vaccine.”

She adds that even the yearly flu shot can affect the lymph nodes. “Every year, flu vaccine season corresponds with breast cancer awareness month, so some patients are getting mammograms when they have enlarged nodes due to the flu shot.”

What happens when the mammogram shows enlarged lymph nodes?

If a mammogram shows that your lymph nodes look large and there’s not an obvious explanation for the change, the radiologist is likely to consider this an abnormal finding. That means you get a call-back: a request to return for further breast imaging such as ultrasound.

Mullen stresses that when it comes to following up on abnormal mammogram results, the patient’s health is the priority, and it’s better to be safe than sorry. At the same time, she acknowledges that getting a call-back can cause a patient anxiety, confusion and inconvenience.

And it’s not just one follow-up. “At the return appointment, we perform an ultrasound of the underarm, get a medical history and measure the lymph nodes,” Mullen says. “After that, the patient needs to follow up with another ultrasound in three months so we can make sure the nodes return to normal size.

“Abnormal-appearing lymph nodes on a mammogram can set off a chain of testing that is expensive and anxiety-producing.”

She says that extra call-backs due to temporary effects of the COVID-19 vaccines can affect patient scheduling at mammogram clinics. When patients require two follow-ups or a biopsy to ensure their lymph nodes are OK, it can make it tougher for other patients to get timely appointments.

Mullen says that many who are first in line to get COVID-19 vaccinations — older women, health care workers, teachers and others — are over age 40 and therefore recommended for yearly screening mammograms.

Scheduling Your COVID-19 Vaccine and Your Mammogram

Mullen says the Johns Hopkins Division of Breast Imaging is following guidelines from the Society of Breast Imaging: Screening mammograms (regular yearly mammograms for patients without symptoms) should be scheduled before your first dose of a COVID-19 vaccination or four to six weeks after the second dose. That way, there is time for your nodes to return to their normal size.

When you call to schedule your mammogram, your breast imaging center might ask you whether you have received a COVID-19 vaccine or have an appointment to get one and schedule your mammogram outside of that timeframe.

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At Johns Hopkins Medical Imaging, your health and safety are our top priority.

Which is a higher priority? Getting your COVID-19 vaccine or getting your mammogram?

Mullen says it depends on whether or not you’re coming in for a regular screening mammogram (your regular check-up when you’re not experiencing symptoms), or a diagnostic mammogram (looking for the cause of symptoms, like a breast lump or breast pain).

She recommends, “If you’ve already had one or both COVID-19 shots, we recommend scheduling screening mammograms four to six weeks after the last shot, since your lymph nodes can become enlarged from the vaccine and may take a while to go down. In this case, it’s OK to delay your mammogram.

“However, if you have any symptoms such as breast pain, a breast lump, nipple discharge or a doctor referral saying you need a diagnostic mammogram, don’t delay: Get the test.”

She notes that her clinic is seeing some patients coming in for diagnostic mammograms to evaluate pain or swelling in the underarm, and it turns out that they’re having lymph node enlargement related to the COVID-19 shot. In this case, she says. “We evaluate the area of concern, reassure the patient and recommend appropriate follow-up.

“If you have any symptom in the breast, do not delay,” she emphasizes.

What happens if I do go for my mammogram within six weeks of getting a coronavirus vaccine?

If you go ahead with getting your mammogram within six weeks of your COVID-19 vaccination and larger-than-usual lymph nodes show up on the test, you will get a call-back for more tests. The doctor may follow up with an ultrasound of the lymph nodes under your arm and request that you come in again in one to three months after that to be sure the lymph nodes return to their normal size.

If you get a mammogram within the first six weeks after your COVID-19 vaccinations and your mammogram is negative for signs of breast cancer and does not show any enlargement of the lymph nodes, your results are considered reliable that there are no signs of breast cancer.

What’s the most important thing to know about mammograms and the COVID-19 vaccine?

“The most important thing patients should understand is that there is no danger of breast cancer associated with the COVID-19 vaccine, and you should plan on getting your vaccines as soon as you are eligible,” Mullen says.

“We’re doing our best to educate patients and avoid unnecessary recalls, tests and anxiety. We want patients to rest assured that a temporary enlargement of the lymph nodes after the COVID-19 vaccine just means the immune system is doing its job.”

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Published March 29, 2021