Screening mammograms and COVID-19 vaccines are both very important for your health. It turns out that timing these two health essentials so they are at least four weeks apart will help you get a more accurate mammogram reading.

Here’s why. As part of the normal immunity-building response to the COVID-19 vaccine, some women who receive the vaccine temporarily experience swollen lymph nodes under their arm on the same side as their vaccine injection.

This is a normal reaction to the vaccine, and the mild swelling typically goes away in just a few days or weeks. To be sure your mammography scan is not affected, it’s best to try to schedule your screening mammogram either before your first COVID-19 vaccine dose or at least four weeks after your second vaccine dose. This reduces the chance that temporarily swollen lymph nodes from the vaccine will appear on your mammogram, so you can avoid the need for follow up scans.

Why does this matter?

Breast radiologists look closely for any changes in your mammogram. Swollen lymph nodes under one arm can be seen on a mammogram and can make it more difficult to get a clear reading.

If you’ve recently received the COVID-19 vaccine, your scan may show swollen lymph nodes that are simply a temporary and normal side effect of the vaccine — a false positive of sorts — so it is important to keep your healthcare provider and screening technician informed.

What happens if there are swollen lymph nodes on my mammogram?

Depending on your medical history and when you received your vaccine, the breast radiologist may recommend you return for an ultrasound of your underarm area. They may also recommend a follow-up scan to see if the lymph nodes have returned to normal size.

When should I schedule my screening mammogram?

Try to schedule your screening mammogram either before your first COVID-19 vaccine dose or at least four weeks after your second vaccine dose. This reduces the chance that temporarily swollen lymph nodes from the vaccine will appear on your mammogram.

What if my appointment for my COVID-19 vaccine and mammogram are already scheduled?

Keep your vaccination appointment. Getting vaccinated is critical to stop the spread of COVID-19.

Consider rescheduling your screening mammogram, if possible, before your vaccine. However, if you are already overdue for your screening exam or cannot reschedule within the next few months, keep your screening mammogram appointment and keep your COVID-19 vaccination appointments.

Regular screening mammograms ensure that breast cancer can be detected as early as possible. Both are very important to ensure that you stay healthy. It's especially important to keep your mammogram appointment if you are significantly overdue for screening.

Remember, annual mammogram screening are an essential step to keep you healthy.

What should I tell the technologist on the day of my screening mammogram?

Notify your mammography technologist if you have received a COVID-19 vaccine. Tell them when you received the vaccine and which arm the vaccine was given. State whether it's your first or second dose.

This information will help the breast radiologist interpreting your screening mammogram.

What if I have other breast problems?

If you have any changes in your breast or underarm — such as pain or a lump — contact your medical provider.

The guidelines above are only for women with no breast symptoms who are scheduled for a COVID-19 vaccine.