Doctors not surprised to find swelling on mammograms after COVID-19 vaccine Doctors notice COVID-19 vaccine causing concerning signs in mammograms By Bethany Davis | March 5, 2021 at 5:53 AM CST - Updated March 5 at 3:02 PM MONTGOMERY, Ala. (WSFA) - Doctors are noticing an interesting side effect of the COVID-19 vaccine thatâs impacting mammograms for women. âRecent studies have shown that approximately 10 to 15 percent of COVID-19 vaccinated patients can have lymph node swelling,â said Dr. Lauren Thorington, a radiologist at the Montgomery Cancer Center. Thorington explained that swelling of the lymph nodes is often caused by cancer. âIn advanced breast cancer, we see enlarged lymph nodes pretty commonly. If itâs an early breast cancer, there should be no enlarged lymph nodes,â Thorington said.