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CLEVELAND (WJW) — Local doctors are reporting a surprising side effect of the COVID-19 vaccine that mirrors a symptom of breast cancer.

“We have been seeing swollen lymph nodes for a couple weeks now,” said Dr. Holly Marshall with University Hospitals.

Marshall says breast radiologists have encountered axillary adenopathy, also known as swollen lymph nodes, on screening mammograms of patients who have been vaccinated.

It’s a surprising side effect that could be mistaken for breast cancer.

“It’s actually a normal response that the body has to the vaccine,” said Marshall.

Marshall says doctors made the discovery because the lymph nodes seen under the arm are included on a mammogram. Patients can also feel them.

Marshall says the swollen lymph nodes are on the same side as the placement of the vaccine.

“We also see swollen lymph nodes in patients with breast cancer, so that’s the concern there.  So we are asking everybody who is having a mammogram if they had the COVID-19 vaccine, what dose, when, and what side?” said Marshall.

Marshall says UH’s Radiology and Breast Cancer Imaging Department has received increased calls from women concerned over the signs.

“It means that the body is making antibodies to fight the COVID-19 infection,” said Marshall.

According to data from the Centers for Disease Control & Prevention, over 11 percent of vaccine recipients experience swollen lymph nodes after one dose, and 16 percent do so after the second dose.

 “This definitely came as a surprise.  Sometimes with other vaccines, occasionally we will see swollen lymph nodes, but it was a surprise how many we’ve been seeing,” said Marshall.

 Marshall says patients are seeing swollen lymph nodes two to four days after the vaccine and they decrease in size after two to four weeks.  If they persist longer than that, Marshall says they need to
be evaluated.

“This really shows the importance of women getting an annual mammogram screening starting when they are 40-years-old.  Do not delay,” said Marshall.