If You Have This One Booster Side Effect, Tell Your Doctor, Experts Say

This vaccine reaction could cause concern if your doctor doesn't have a warning.

Side effects of the COVID shots are common and widely documented, and the booster doses currently being doled out are no exception to vaccine reactions. The Centers for Disease Control and Prevention (CDC) lists sore arm, fatigue, chills, headache, and fever among the more unpleasant ones that many people experience. 

But there's one less discussed side effect of the shot that can spook you if you're not expecting it. That's why you should know that swollen lymph nodes can result from vaccination. It's nothing to fear: It's temporary, and in fact it's among the signals that the vaccine is working to develop an immune response in your body. But it's still a possibility, and it seems to show up slightly more often after booster shots. A recent report from the U.S. Food and Drug Administration (FDA) identified lymphadenopathy as a more common side effect after a booster than the initial vaccine doses.

RELATED: Half of Moderna Booster Recipients Have These 4 Side Effects, CDC Says.

While harmless, this side effect can be particularly alarming if it shows up in a mammogram. That's why you should make sure your doctor knows about your recent vaccination ahead of time.

"If you are a woman, and you're going to get a mammogram, and you get your booster shot, call and tell them you're getting it [or] you've gotten it," Peter Marks, MD, head of the FDA's Center for Biologics Evaluation and Research, explained at a town hall, per CNN.

Letting your doctor or the technician know upfront about your recent shot will allow them to flag the issue and more easily interpret the results of your imaging. If possible, you might even time your shot so it follows your scheduled mammogram and avoid the issue altogether, Marks suggests.

"If you're going to get it, you might want to get your mammogram first before you get it, or you might want to wait a couple of weeks because if those lymph nodes turn up on a mammogram, they may trigger a false, further investigation," he said. "It's really a harmless thing, except if it triggers extra medical investigation, so that's just something to be aware of."

The Mayo Clinic recommends going forward with any scheduled mammograms as normal, without any delay around your vaccine schedule. "But be sure to tell your doctor about your vaccination, the date it occurred, and which arm was affected. This information will be helpful for understanding the mammogram images," explains Sandhya Pruthi, a Mayo Clinic internal medicine doctor with special interests in breast diseases and women's health. "If lymph node swelling is found on your mammogram and you've recently received the COVID-19 vaccine, the doctor who interprets your mammogram images (radiologist) will consider this when recommending whether additional imaging or follow-up is needed."

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It's essential to note that the COVID vaccine does not cause cancer or increase your risk for getting it. "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," Lisa Ann Mullen, MD, breast imaging fellowship director and assistant professor of radiology and radiological science, explains on the Johns Hopkins Medicine website. "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."

It's also not just the vaccines for COVID-19 that can trigger swollen lymph nodes. You might expect a similar response from some other vaccines, including the flu shot, the shingles vaccine, and the diphtheria/tetanus/pertussis (D-TaP) shot.

RELATED: 70 Percent of People Who Get a Pfizer Booster Have This Side Effect.

Alesandra Dubin
Alesandra Dubin is a lifestyle editor and writer based in Los Angeles. Read more
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