Mammograms are a widely used imaging tool that helps detect breast changes, including potential cancer. Vaccines stimulate the body’s immune system to fight specific diseases. A common question is whether vaccination can influence mammogram screening results. It is helpful to understand how vaccines interact with the body and how this interaction might appear on a mammogram.
How Vaccines Affect Mammogram Results
Vaccines can affect mammogram results by causing temporary enlargement of lymph nodes, known as axillary lymphadenopathy. This effect is typically observed in the armpit, or axillary, area on the same side of the body where the vaccine was administered. This swelling can appear on imaging, potentially raising questions during a mammogram. COVID-19 vaccines, flu shots, and tetanus shots are frequently reported to cause this temporary lymph node swelling. The incidence of axillary lymphadenopathy after COVID-19 vaccination has been reported to range from 2.4% to 35% in women undergoing screening mammography, a notable increase from the 0.02%–0.04% incidence seen before the pandemic.
Why Lymph Nodes Swell After Vaccination
Lymph nodes are small, bean-shaped glands in the body’s immune system, acting as filters that trap harmful substances like bacteria and viruses. When a vaccine is introduced, lymph nodes activate to produce white blood cells and antibodies, essential for fighting infections. This activity leads to the swelling and sometimes tenderness of the lymph nodes closest to the injection site. This enlargement is a normal physiological response, indicating the body is mounting an immune response and building protection. The swelling usually develops within a few days of vaccination and can persist for several weeks, or in some cases, even up to 43 weeks.
Important Considerations for Your Mammogram Appointment
Given potential vaccine-induced lymph node swelling, communicate recent vaccination details during your mammogram appointment. Patients should inform the radiologist or mammography technician about the date of their most recent vaccination and the arm in which it was administered. While earlier recommendations suggested waiting four to six weeks after vaccination, current guidelines from the Society of Breast Imaging (SBI) no longer recommend delaying routine screenings. However, if you have concerning breast symptoms, such as a palpable lump or nipple discharge, do not delay your mammogram regardless of recent vaccination.
Understanding Mammogram Findings After Vaccination
Swollen lymph nodes detected after vaccination are almost always benign, indicating a functioning immune system rather than cancer. Radiologists are aware of this common occurrence and differentiate between vaccine-related swelling and findings suggesting malignancy. If vaccine-related lymph node swelling is identified, a healthcare provider might recommend a follow-up ultrasound or mammogram, typically after 12 weeks, to confirm resolution. This follow-up is a precautionary measure to ensure swelling resolves and rule out other possibilities, but it does not imply a higher breast cancer risk.