Getting vaccinated for COVID-19 is an important way to protect yourself from potentially serious effects of the coronavirus. Likewise, getting regular mammograms as your doctor recommends can keep you safer by catching breast cancers early, when they might be easier to treat.

There is no connection between the COVID-19 vaccine and breast cancer. But what should women know about how the COVID-19 shots might affect the results of their mammograms? Lisa Mullen, M.D., a radiologist who specializes in breast imaging, offers some perspective and answers your questions.

How do vaccines, including the COVID-19 vaccine, affect lymph nodes?

Mullen says, “Lymph nodes under the arm where a person has gotten a vaccine can become enlarged as part of the normal immune response to the vaccine.”

Not all vaccines cause swollen lymph nodes, but ones that cause a more intense immune response, such as the COVID-19 vaccine, some shingles vaccines, and others, are more likely to affect them. “The COVID-19 vaccine is a new type of vaccine, and people are reacting strongly to it,” Mullen says. “That heightened immune response is normal and expected.”

She adds that even the yearly flu shot can affect the lymph nodes. “Every year, flu vaccine season corresponds with breast cancer awareness month, so some patients are getting mammograms when they have enlarged nodes due to the flu shot.”

That being said, the Society of Breast Imaging and the Johns Hopkins breast imaging division do not recommend a delay between receiving the vaccine and scheduling your screening mammogram.

Why have the guidelines changed?

During the winter of 2021, the Society of Breast Imaging released conservative guidelines related to COVID-19 vaccines and screening mammograms. The recommendations — based on the limited information available at that time — included a four- to six-week delay between receiving a vaccine and getting a screening mammogram, as well as other suggestions for management of enlarged lymph nodes.

Since that initial release, multiple studies have been published about this topic. It is now understood that enlarged lymph nodes from a COVID-19 vaccine can be seen over a long period of time, up to several months. After reviewing the new information, the Society of Breast Imaging released updated guidelines in February 2022. The new recommendation is no delay between a vaccine and a screening mammogram.

What should I expect when scheduling my mammogram?

During the scheduling process and before your exam, you may be asked if you have received a COVID-19 vaccine, the date you received it, and in which arm it was given.

What’s the most important thing to know about mammograms and the COVID-19 vaccine?

“The most important thing patients should understand is that there is no danger of breast cancer associated with the COVID-19 vaccine, and you should plan on getting your vaccines as soon as you are eligible,” Mullen says.

“We’re doing our best to educate patients and avoid unnecessary recalls, tests and anxiety. We want patients to rest assured that a temporary enlargement of the lymph nodes after the COVID-19 vaccine just means the immune system is doing its job.”