Getting a mammogram soon after getting the COVID-19 vaccine? Be warned: The vaccine might cause your lymph nodes to swell, which may be confused for a sign of breast cancer. “Getting the COVID-19 vaccine can cause temporary lymph node enlargement and result in a ‘false positive’ mammogram,” Lisa Ann Mullen, MD, explained in an article published by Johns Hopkins Medicine on the topic. The enlargement may cause “your mammogram to appear abnormal even when you are OK and there is no indication of cancer.” While the reaction is “nothing to worry about” and is a common effect of all vaccinations, it has caused a rise in swollen armpit lymph nodes on multiple types of breast imaging, leading many women to have additional testing, and sometimes even biopsies, as well as “unnecessary stress and anxiety,” Penn Medicine wrote in a post. To avoid unnecessary further testing or distress, the Centers for Disease Control and Prevention advises that people ask their doctors how long they should wait before getting a mammogram after being vaccinated. “Some experts recommend getting your mammogram before being vaccinated or waiting four to six weeks after getting your vaccine,” the CDC adds.