A woman undergoing a mammogram.
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.
The swelling may 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.