Like all vaccines, the two new coronavirus vaccines in use aggravate a human body's defense against an invader.  Signs of that response can include fever, aches and sometimes swelling of lymph nodes.  These are normal reactions to a vaccine and a sign that your body is doing what it needs to do in order to fight off the virus should it come in contact with it.

Lymph nodes are small clumps of tissue that collect and transfer fluid called lymph that filter toxins and helps fight infection.  During clinical testing, the COVID-19 vaccine stimulated such a strong response in some women that swollen armpit lymph nodes showed up on mammograms.  Breast imaging radiologists see normal lymph nodes all the time, but every so often, a mammogram shows abnormal lymph nodes.  When it does, additional testing may be ordered to rule out lymphoma.

The Society of Breast Imaging (SBI) reported that 11.6% of women who received the first dose of the Moderna vaccine during last year's clinical testing in 40,000 Americans had swelling of the lymph nodes in the armpit.  After the second dose, 16% of women reported the swelling.  The results in clinical testing for the Pfizer vaccine were less severe, with 70 total cases reported from among 40,000 Americans.  Any swelling of lymph nodes arrived within four days of vaccination and lasted as long as 10 days.  The society's guidelines also said reports of swelling came from patients, so the actual number of people who had swollen lymph nodes with either vaccine is probably higher.

Because of the higher rate of lymph node swelling the COVID vaccine can cause, South Sound Radiology Breast Center and VanRad-Vancouver Village Breast Center are following the SBI guidelines suggesting that women wait at least 10 days after their second COVID vaccine before having their mammogram.  To learn more about the SBI COVID vaccine study and recommendations, please click here.