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COVID Vaccine Could Cause Swelling Mistaken For Breast Cancer

a short haired person with their back turned to the viewer gets their breast imaged on a mammogram machine
peakSTOCK/Getty Images/iStockphoto
Senior woman having a mammography scan at hospital

Common reported side effects of the COVID-19 vaccine have been body aches, nausea, chills and headaches. But one side effect could be mistaken as a possible sign of cancer.

Radiologists at Moffitt Cancer Center in Tampa are warning that the Moderna and Pfizer-BioNTech coronavirus vaccines can temporarily interfere with mammogram results.

They can cause swollen lymph nodes in the armpit on the side where the vaccine was administered.

Dr Bethany Neill, the section chief of breast imaging at Moffitt, said this can also be a very rare presentation of breast cancer.

"My colleagues and I have experienced this issue already, not only in the screening setting, but also in women who have been recently diagnosed with breast cancer. Both of those groups of women may receive COVID vaccine doses."

Neill said the swelling could last for days or weeks after the vaccine as part of the immune response it elicits.

For patients receiving the Moderna COVID-19 vaccine, axillary swelling or tenderness was reported in 11.6% of patients following one dose and 16% of patients following the second dose. In the Pfizer-BioNTech COVID-19 trial, the side effect was reported in 58 more cases in the vaccinated group than the placebo group.

To avoid any false red flags, Neill said people should schedule their mammogram before they get vaccinated or wait four to six weeks after.

But she warns against delaying mammograms for too long.

"The COVID pandemic is resulting in delayed cancer diagnoses and will likely cause unnecessary deaths from breast cancer over the next several years."

Breast radiologists believe they will continue to see lymph node swelling as more and more patients become vaccinated, so the Society of Breast Imaging has established recommendations to manage it in patients who have been vaccinated recently.

Those recommendations include a follow-up visit four to six weeks after the second vaccine dose, potentially with additional imaging. If the swelling persists, a biopsy might be needed for further testing.


I took my first photography class when I was 11. My stepmom begged a local group to let me into the adults-only class, and armed with a 35 mm disposable camera, I started my journey toward multimedia journalism.
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