CLEVELAND (WJW) — Doctors are reporting a 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 Cleveland Medical Center.

“It’s actually a normal response that the body has to the vaccine,” said Marshall. “It means that the body is making antibodies to fight the COVID-19 infection.”

Marshall said breast radiologists have encountered axillary adenopathy, also known as swollen lymph nodes, on screening mammograms of patients who have been vaccinated. It’s a side effect that could be mistaken for breast cancer.

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

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

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

“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 said 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 said 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.