If you’ve ever experienced swollen lymph nodes, you know how uncomfortable (and temporarily concerning) their presence can be. After all, when lymph nodes—small, bean-shaped glands throughout your entire body—become enlarged, it’s typically a sign that your immune system is reacting to something it perceives as a threat.
With the COVID-19 vaccine, that “something” is a sign that your body is being primed to recognize the novel coronavirus once your immunization is complete—meaning you might experience uncomfortable but short-lived side effects, particularly after the second dose in a two-part series. This can include arm swelling and soreness around the injection site, a mild fever, headaches, chills, and yes, possibly even swollen lymph nodes.
In fact, the Society of Breast Imaging (SBI) issued a recommendation earlier this year that women should wait to get a mammogram after their COVID-19 vaccine because lymph node swelling in the armpit caused by the vaccine could be mistaken for breast cancer.
However, rest assured that swollen lymph nodes are just a sign that your immune system is getting to work post-vaccine, says Jamie Alan, Pharm.D., Ph.D., associate professor of pharmacology at Michigan State University.
But what do these glands look and feel like? And how long will the swelling last if you experience this annoying side effect? Ahead, experts explain what to expect.
First, a brief primer on why lymph nodes swell.
Your immune system contains a network of lymph vessels and lymph nodes. They make up your lymphatic system, which collects fluid, waste, viruses, and bacteria that travel into your tissues outside of your bloodstream, according to the American Cancer Society (ACS).
Your lymph vessels are a bit like blood vessels. But instead of blood, they contain a clear, watery fluid (a.k.a. lymph fluid). The main job of this fluid is to fight infections with the assistance of white blood cells. So basically, our lymph nodes work as filters for potentially harmful substances, the ACS says.
If you do happen to have an infection, an injury, or a disease like cancer, the nodes—say, in your neck, in your armpit, under your chin, or around your groin—can swell or enlarge as they attempt to filter the harmful stuff out of your body.
Are swollen lymph nodes a common side effect of the COVID-19 vaccine?
The SBI’s report cited data that found up to 11.6% of patients who received the Moderna COVID-19 vaccine had swollen or tender lymph nodes after the first dose, while 16% of patients experienced it after their second shot. The side effect was not as common in those who received the Pfizer-BioNTech vaccine, but it was still reported among those patients.
You can technically get swollen lymph nodes anywhere, but you’ll most likely notice them under your arms and in your neck if they appear post-vaccine, says infectious disease expert Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security. “It’s usually around the areas where the injection was,” he says, and it will feel like a soft, tender lump.
It’s also important to note that this side effect isn’t unique to the COVID-19 vaccine, and can even happen with the flu shot, says William Schaffner, M.D., an infectious disease specialist and professor at the Vanderbilt University School of Medicine.
Because the COVID-19 vaccine is newly developed and we’re all much more aware of potential side effects (and our health after a stressful year), we may “simply be paying more attention to our bodies,” Dr. Schaffner says, resulting in more frequent reports.
How long do swollen lymph nodes last after the COVID-19 vaccine?
The SBI’s report found that those who experienced swollen lymph nodes could have them up to 10 days post-vaccine on average. But everyone’s body is different, and the swelling can last about a week, possibly longer. “Swollen lymph nodes will usually get progressively smaller,” Dr. Adalja says.
Can you treat swollen lymph nodes?
If your swollen lymph nodes aren’t bothering you, you don’t necessarily need to treat them as they reduce in size on their own. But if you’re uncomfortable, Alan says that you can use heat on the area (think: a warm, damp washcloth). You can also take an OTC medication like acetaminophen or ibuprofen to help reduce pain and inflammation.
Of course, it’s important to keep in mind that your swollen lymph nodes might be due to something else going on in your body. If they popped up right after your vaccine, it’s very likely linked to that—but they should start to settle down in about a week or so. If they persist any longer or feel especially hard, Dr. Schaffner recommends calling your doctor. “Something else might be involved,” he says, and it’s best to get things checked out to ensure a proper diagnosis.
This article is accurate as of press time. However, as the COVID-19 pandemic rapidly evolves and the scientific community’s understanding of the novel coronavirus develops, some of the information may have changed since it was last updated. While we aim to keep all of our stories up to date, please visit online resources provided by the CDC, WHO, and your local public health department to stay informed on the latest news. Always talk to your doctor for professional medical advice.
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