The Rare COVID Vaccine Side Effect Doctors Want You to Prepare For

This potential side effect hasn't been as widely discussed as others.

COVID vaccinations kicked off in December in the U.S., and they have been steadily reaching more and more people as the weeks have gone on. But even before the vaccines were being administered in the States, medical experts were warning Americans to prepare for some noticeable side effects post-shot. According to the Centers for Disease Control and Prevention (CDC), the expected vaccine side effects—fever, chills, tiredness, headache, and pain or swelling of the injected arm—are a normal response to your body building immunity against the virus. But now, doctors are warning about another vaccine side effect that hasn't been as discussed. As more and more people get their shots, they're noticing a lump in the armpit of the arm where they got vaccinated. While this might seem strange or alarming, doctors want to assure patients that it's actually totally normal, even though it's on the rare side as far as side effects go. Read on to find out more about this reaction and for another heads-up about vaccinations, know that This COVID Vaccine Side Effect Could Show Up a Week After Your Shot.

Some patients are reporting a lump in their armpit after getting the COVID vaccine.

Armpit pain

Recently, people who have been vaccinated are sharing stories online about feeling lumps in their armpits, which might seem like cause for concern, but is in fact, to be expected. In a CDC report on the Moderna vaccine, the agency said that the swelling of lymph nodes, also known as lymphadenopathy, can occur in either the arm or the neck. And if you're preparing for your shot, know that If You Take These OTC Meds, You Have to Stop Before Getting the Vaccine.

They tend to appear a few days post-vaccination.

Closed up the on man's next, who is examining lymph nodes
kwanchaichaiudom / iStock

According to the CDC's report, these lumps typically appear two to four days after your vaccination, but only last about one to two days.

Based on the CDC's findings, this vaccine side effect is quite rare. "Reports of lymphadenopathy were imbalanced with 1.1 percent of persons in the vaccine group and 0.6 percent in the placebo group reporting such events," the CDC notes. And for more vaccine news to know, find out why If You're Over 65, You Shouldn't Get This New Vaccine, Experts Warn.

Doctors say this is a normal side effect of the COVID vaccine.

Older man getting COVID vaccine

Purvi Parikh, MD, an immunologist with Allergy & Asthma Network and a co-investigator on COVID-19 vaccine trials at NYU, told Popsugar that swollen lymph nodes are just one way in which your body may show that it is building an immune response. There are immune cells in your lymph nodes that are activated by the vaccine, and the ones near your armpit may be the most prone to swelling because they're typically the closest to your injection site, Parikh explained.

In fact, the U.S. Food and Drug Administration (FDA) says you should expect the possibility of "swollen lymph nodes in the same arm as the injection" for both the Moderna and Pfizer vaccines. And for more up-to-date COVID news delivered right to your inbox, sign up for our daily newsletter.

But call your doctor if the swelling doesn't subside after a few days.

Senior patient waiting for vaccination while young female doctor pulling COVID-19 vaccine from vial with syringe. Focus on vial with vaccine and doctor´s hand with syringe.

According to Parikh, swollen lymph nodes are not one of the most common side effects, but it's not one that should cause alarm. According to the CDC, the only instances in which you may need to contact your doctor or healthcare provider is if the redness or tenderness where you got the shot increases after 24 hours or "if your side effects are worrying you or do not seem to be going away after a few days." And for more helpful tips from the CDC, discover why The CDC Doesn't Recommend This One Type of Face Mask.

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