After a COVID-19 vaccination, a person's underarm lymph nodes may become swollen on the same side of the body where they had the injection. That's normal. In fact, it's a sign that the immune system is responding to the vaccine. However, the swelling may also show up on mammogram images.
Breast imaging experts aren't surprised when it does.
"We've seen it before with other vaccines, such as the shingles vaccine (or) the flu vaccine," says Dr. Stamatia Destounis, a radiologist at Elizabeth Wende Breast Care in Rochester.
She says swollen lymph nodes resulting from a vaccine typically shrink back to their normal size within a few weeks.