• Aches and fever are common side effects of coronavirus vaccination. But will taking acetaminophen or ibuprofen affect how well the vaccine works?
  • The side effects show that the vaccine is teaching your immune system how to recognize and attack SARS-CoV-2, the coronavirus that causes COVID-19, if it encounters it.
  • Experts say do not take pain relievers before your vaccine.

The coronavirus vaccine helps protect you from getting COVID-19. It can also prevent you from having the long-lasting health problems experienced by some COVID-19 patients, or “COVID-19 long haulers.”

As with all vaccines, you may have some side effects, such as pain or swelling at the site of the injection, fever, chills, tiredness, or headache.

Dr. David J. Cennimo, an infectious disease physician and assistant professor at Rutgers New Jersey Medical School, said these are “signs of an appropriate recognition and immune reaction to the vaccine.”

The side effects show that the vaccine is teaching your immune system how to recognize and attack SARS-CoV-2, the coronavirus that causes COVID-19, if it encounters it.

Although some of the vaccine side effects are similar to the symptoms of COVID-19, the coronavirus vaccines won’t give you COVID-19. The vaccines will also not make you contagious.

For most people, the side effects of the vaccine are mild or moderate and last only a day or two. However, for some people the side effects make them feel like they have the flu, or affect their ability to perform daily activities.

Faced with a couple of days of flu-like discomfort, many people — including physicians — will reach for an over-the-counter medication such as ibuprofen (Advil, Motrin) or acetaminophen (Tylenol) to relieve their fever and pain.

But if these drugs reduce the side effects of the vaccine, is there a chance that they’ll also depress the immune system’s beneficial response to vaccination?

No research has been done to look specifically at whether acetaminophen or ibuprofen can interfere with how well the coronavirus vaccine works.

But Cennimo said some earlier research suggests that some drugs may affect the immune response to vaccines.

“There are data in the vaccine literature, long predating COVID-19 and almost all [done] in children, that premedication with [fever-reducing drugs] like acetaminophen or ibuprofen decrease the antibody response to the first dose of vaccine,” Cennimo said.

Parents would sometimes give their child a pain reliever before their vaccine injection to head off the discomfort.

Cennimo said it’s not known how these medications interfere with vaccines, but the drugs may dampen the inflammatory response — which shows up as fever and aches.

With less inflammation, he said, there may also be a lower immune response to the vaccine.

More recently, a study published this month in the Journal of Virology found that nonsteroidal anti-inflammatory drugs (NSAIDs) — which include ibuprofen — reduced the production of antibodies and other aspects of the immune response to SARS-CoV-2.

Antibodies are proteins made by the immune system to fight viruses like SARS-CoV-2. The COVID-19 vaccines stimulate the body to produce antibodies that specifically target the coronavirus without causing disease.

The authors of this study said that this raises the possibility that NSAIDs might also affect the immune response to coronavirus vaccination. But additional studies would be needed to know for certain.

Some earlier research in the laboratory suggests that fever-reducing pain medications may blunt the antibody response to vaccination, but it’s not clear what this means in the real world.

More research is needed, of course. But COVID-19 vaccine studies that have already been done suggest that taking a pain reliever after injection, if needed, may not cause that much of a problem.

The protocols for the late-stage clinical trials of the Pfizer-BioNTech and Moderna-NIAID coronavirus vaccines didn’t prevent people from taking pain-relieving medications if they felt they needed it.

Even with that, those studies still showed that both vaccines have a high efficacy rate: 95 percent for Pfizer-BioNTech and 94.1 percent for Moderna-NIAID.

In spite of the need for more data, Cennimo doesn’t think there’s a problem with taking ibuprofen or acetaminophen after your coronavirus vaccine injection, as long as you don’t exceed the recommended amount.

He had his second dose of the coronavirus vaccine last week and took ibuprofen afterwards for a low-grade fever and some aches.

As for whether you should try to preempt your vaccine side effects with a pain reliever, Cennimo advises against it.

“In the COVID-19 vaccine trials, people were not given an NSAID or acetaminophen before the injection, so we do not know what — if any effect — premedication would have,” he said. “Because of these theoretical risks, it is not advised.”

Cennimo said the pre-COVID-19 vaccine research in children found that taking a fever-reducing drug only affected the production of antibodies if the drug was taken before the injection.

Dr. Sherrill Brown, medical director of infection prevention at AltaMed Health Services, a federally qualified healthcare center serving Los Angeles and Orange counties in California, agrees.

“I would recommend waiting until someone experiences side effects of fever or pain that require fever-reducing or pain-reducing medications,” she said, “and not to take them as a prophylaxis to prevent vaccine related symptoms.”

The Centers for Disease Control and Prevention (CDC) issued similar guidelines for how to deal with the side effects of the two mRNA vaccines that have been approved in the United States.

Brown also cautions that even over-the-counter pain relievers may not be appropriate for everyone.

“Some people are not able to take either acetaminophen or ibuprofen due to other underlying health conditions,” she said. “In those cases, it would be best to consult with their trusted healthcare provider or physician before taking these medications.”

If you can’t take pain relievers, or you would like to avoid taking them after your coronavirus vaccine injection, there are other ways to relieve vaccination side effects.

To reduce pain and discomfort at the site of injection, apply a cool, wet washcloth over the area to reduce the swelling. Gently exercising the arm also increases blood flow to the area which can provide additional relief.

For fever, drink plenty of fluids, wear light pajamas or clothing, sponge your body with lukewarm (not cold) water, and eat popsicles. And of course, rest.

If your fever lasts longer than 3 days, or reaches 103°F (39°C) or higher, seek medical care. Seek treatment right away if you develop a rash, difficulty breathing, or chest or abdominal pain.