You can safely take pain medication to treat symptoms after getting the COVID-19 vaccine, say experts. Headaches, fever, body aches, and chills are normal side effects of the vaccine and could mean that your immune system is working. However, experts warn that taking pain medications or non-steroidal anti-inflammatory drugs (NSAIDS) before getting the vaccine may reduce the effectiveness of the drugs.

According to USA Today, both the Centers for Disease Control and Prevention and the World Health Organization agree that it is okay to take pain relievers after the vaccine if symptoms become bothersome, but recommend against their use as a precautionary measure. Research has shown that taking anti-inflammatory drugs such as ibuprofen can reduce the production of antibodies and could alter the immune response.

Dr. Kerry McGee, M.D. says that while both the Pfizer and Moderna vaccines have been found to be safe and effective, taking steroids or anti-inflammatory drugs can reduce the effectiveness.

In an article she wrote for GoodRx, McGee said that researchers have found that taking the fever-reducing drug acetaminophen, which is Tylenol, has been found to produce a lower immune reaction to vaccines in children.

“For the COVID-19 vaccine, it seems likely that the same thing will happen,” she says. “The vaccine’s effect will be slightly less in people who are taking anti-inflammatory or immunosuppressant medications than it will be in those who aren’t taking those medications. But especially for people who need to take these medicines, some immunity against COVID-19 is better than none.”

Dr. Paul Offit, an infectious disease expert and a member of the Food and Drug Administration’s COVID-19 advisory panel, says that taking fever-reducing medicines like aspirin, acetaminophen and ibuprofen can reduce the effectiveness of the vaccines by interfering with the immune response. He “definitely recommends” that people avoid taking antifever drugs around the time of vaccination, according to AARP.

Although there is no data that indicates a reduce immune response if pain relievers are taken after the shot, says Dr. Colleen Kelley, an infectious disease expert at Emory University School of Medicine.

“It’s perfectly fine to take NSAIDS or Tylenol if you are feeling unwell after vaccination,” she told USA Today. “The symptoms you are experiencing indicate that your immune system is functioning normally, and that the immune response is ongoing.”

Dr. Mahyar Etminan, however, an epidemiologist at the University of British Columbia, suggests that people do not take any pain killer within at least 6 hours of getting their COVID-19 vaccine.