It’s common for mammograms to pick up swollen lymph nodes, also known as lymphadenopathy, after vaccination, said the study, published Tuesday in the journal Radiology. Swollen lymph nodes following a vaccination are a short-term, harmless sign that the vaccine is working.
Many people noticed swollen lymph nodes after Covid-19 vaccines were rolled out, but they can also happen with other vaccinations, such as a flu shot or shingles vaccine.
Some doctors suggested that patients who recently got vaccinated and had swollen lymph nodes may want to wait a few weeks before getting a mammogram, but others have said it’s important not to skip or delay mammograms or vaccinations.
“It is important for people to know that they should not delay their screening mammograms due to recent vaccination. Reactive lymphadenopathy is common after COVID-19 vaccination — and benign,” said study author Dr. Stacey Wolfson, of the Department of Radiology at New York University Grossman School of Medicine and NYU Langone Health, in a statement.
In the study, 537 of the 1,217 people who received Covid-19 vaccination and underwent breast imaging had lymphadenopathy. Swollen lymph nodes were found in 46% of those who got the Moderna vaccine, 38% of those who got the Pfizer vaccine and 39% of those who got the Johnson & Johnson vaccine.
The swollen lymph nodes were most commonly seen in the first two weeks after vaccination but can persist much longer.
“I was surprised by how quickly the lymph nodes became swollen and how long they persisted after being detected on routine screening mammogram and screening ultrasound exams,” Wolfson said. “We found benign reactive lymph nodes were still present despite delaying the screening exams for four to six weeks based on various guidelines. These lymph nodes were unchanged with follow up exams at three months, and some enlarged lymph nodes persisted for over 10 months.”
Wolfson said follow-up imaging in people with swollen lymph nodes is not recommended unless there are other suspicious mammographic findings.
Regular mammograms can help identify breast cancer early on. The American Cancer Society says women age 40 to 44 with average risk have the option to start screening every year; women age 45 to 54 should get mammograms every year; and women age 55 and older can switch to mammograms every other year, or continue with yearly mammograms.
“We have recommended that women (if possible) get their yearly mammogram prior to vaccination to avoid any impact from vaccine-related lymph node swelling on mammography interpretation. If a woman has been recently vaccinated, we still advise them to receive a yearly mammogram on their usual schedule, but inform the imaging center staff of their recent vaccination so that this information is factored into the interpretation process,” Dr. Stamatia Destounis, chief of the American College of Radiology Breast Imaging Commission, said in a statement. “The ACR has left the decision regarding follow up frequency to local breast imaging facilities, radiologists and their patients.”