When Sheryl Recinos and her husband volunteered as test subjects in the clinical trial for the Pfizer vaccine in August, they knew immediately that they hadn’t gotten placebo doses. Their arms were not just sore—they really hurt. “I felt like I’d been hit by a truck,” said Recinos, who is a physician in Los Angeles.* This pain continued on for a couple of days.
Arm pain, as you may have heard or experienced yourself, is a typical side effect of the COVID-19 vaccines, and it can take on weird and confusing forms. While some people just have some soreness, others have shooting pain that goes from their arm down the side of the body, pain that travels into their shoulders, or even pain that turns into a tingling in one of their hands. Susan Matthews, Slate’s news director, felt shooting pains all over her body hours after getting the Johnson & Johnson shot. “What was happening to me was what I imagined Polyjuice Potion was supposed to feel like,” she said, referencing the Harry Potter potion that, very painfully, turns the spellbound into someone else.
There’s a pretty simple explanation for why people experience some soreness around the injection site. Ashley Z. Ritter, a postdoctoral fellow at the University of Pennsylvania and the chief clinical officer of Dear Pandemic, says that this is a common side effect—from any vaccine. Injecting the vaccine into the arm muscle stimulates the immune system. “When that fluid goes into the muscle, the body is sending messengers and white blood cells and lymph fluid to that area to build an immune response,” Ritter explains. That’s exactly what you want to happen, but it can be a little uncomfortable. “A lot of the pain that you feel is that sort of activity happening within your body,” Ritter says. The increased fluid in the lymph nodes near the injection site commonly causes muscle pain, and sometimes armpit or breast pain. (And even if you’re pain-free, the swollen lymph node may show up on mammograms, so experts recommend not getting one too soon after you get a shot.)
But what about that shooting, radiating pain that some people report? Both Recinos and Ritter agree this strange sensation is just nerve pain, as opposed to muscle pain. “If you have enough inflammation in the area, you can have nerves that have swelling around them as well that could send a shooting pain down the arm,” Ritter explains. Sometimes, the white blood cells and other messengers involved in the body’s response to the vaccine can enter the bloodstream. That can “set off a cascade of neurological and immune system functions,” Ritter says. Having pain in strange places—even far from your arm—is “a totally normal thing.” In rare cases, you might feel kind of like your body is morphing, but this is not a cause for concern. When the immune response and swelling die down—within hours to a couple days—the pain will go away. If the pain is really bad, Reconis suggests waiting for 12 hours to allow your body to have its full immune response, and then taking ibuprofen or Tylenol. If symptoms are “significantly impacting your ability to function, and if it’s outside of that window of expected side effects, you want to call a health professional,” Ritter says.
These side effects aren’t unique to the COVID vaccine; they can happen with any adult vaccine. But since the COVID vaccine is such a widely shared societal phenomenon, its side effects are front and center in a lot of conversations. “It’s good that people are talking about it,” Ritter says. “Communication about expected immune system revving symptoms is important to maintain trust and transparency with the public.” It also might be helpful to remember that people just vary in how their bodies respond to the vaccine. If you feel like you are the only person you know with specific, weird, post-vaccine woes, it doesn’t mean something is wrong with you, or that you did something wrong before getting your shot. “I sort of think of it as, if you put 100 people on a roller coaster, some of them might experience motion sickness, but not all,” Ritter says. Younger people, who have more active immune systems, seem to have more intense symptoms. But even if you have no symptoms at all, the vaccine is still working. Many people in the clinical trials for the vaccines experienced no side effects at all and were still protected.
And if you are knocked out after the shot with bizarre sensations, just remember the bigger picture. When the vaccine rollout began, Recinos says her colleagues couldn’t stop comparing side effects and obsessing over different body pains. But all around them in the hospital, patients were still dying of COVID. “I’m OK with people having arm pain and headaches and nausea and all those other symptoms because it’s short-lived, and it’s not permanent. But death is permanent,” says Recinos. “Even if we feel miserable, it’s worth it.”
Correction, April 23, 2021: This post originally misidentified Sheryl Recinos as a nurse. She is a physician.
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