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A Timeline of COVID-19 Vaccine Side Effects

COVID vaccination illustration.

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Key Takeaways

  • Most people experience soreness in the arm immediately after being vaccinated and more severe, systemic side effects like fever and chills within 8 to 12 hours. 
  • Most side effects will resolve within 48 hours.
  • It’s not possible to be infected with COVID-19 from the vaccine, so symptoms mean your body is building an effective immune response.

If you’re getting ready to receive the first or second dose of your COVID-19 vaccine, you may be wondering about the kinds of side effects you may experience and how to manage them.

You may feel some side effects immediately after your shot, like tenderness at the injection site. Others may take hours to develop like fever or chills. And keep in mind, for two-dose vaccine regimens like Pfizer-BioNTech and Moderna, side effects tend to be more severe after the second shot.

Illustration of the potential COVID vaccine side effects

Theresa Chiechi / Verywell Health

Here’s a rough timeline of potential symptoms to help you understand what to expect after the jab.

Immediately After Vaccination

The first symptom you may notice is a soreness in your arm where the vaccine was injected. As with any intramuscular vaccine, the syringe will deliver the liquid vaccine into your muscle tissue. Your immune system will recognize this as a threat and create an inflammatory response, potentially causing your arm to become sore, turn red or swell a bit. Some people who receive the Moderna vaccine even experience "COVID arm," or skin reactions that resemble raised, red welts around the injection site.

The COVID-19 vaccines can cause tenderness similar to what some experience after the tetanus vaccination, Michelle Barron, MD, senior medical director of infection prevention and control for the University of Colorado Health, tells Verywell.

To reduce discomfort from the injection site, the Centers for Disease Control and Prevention (CDC) recommends placing a cool, wet washcloth over the area. Moving or exercising your arm can also help minimize the pain.

15 Minutes After Vaccination

The risk of anaphylaxis—a severe allergic reaction to the vaccine—significantly drops 15 to 30 minutes after vaccination. This reaction is very rare, but the CDC requires everyone receiving the vaccine to wait in the vaccination clinic for 15 minutes after receiving the shot, in case of an adverse response.

“If you've had allergic reactions in the past, we want people staying for 30 minutes,” Kate Mullane, DO, PharmD, professor of medicine and infectious disease specialist at the University of Chicago, tells Verywell.

12 Hours After Vaccination

Other side effects begin to appear within a few hours or up to 12 hours after the shot. People commonly report experiencing systemic side effects, like fever, headaches, muscle aches, joint pain, chills, and fatigue.

In the Pfizer-BioNTech vaccine trials, more than 77% of participants reported at least one systemic reaction. The most common were fatigue, headache, and new or worsened muscle pain.

Some less common side effects you may experience include nausea and swollen lymph nodes (especially in the armpit).

But there's no need to worry about these flu-like symptoms. When you experience strong side effects, it means your body is working hard to build the antibodies and cells it will need to fight the virus, should you ever be exposed to it.

“Although you feel terrible, it's a good thing, because those systemic effects are telling you that your body is making an immune reaction,” Mullane says.

12 to 48 Hours After Vaccination

Once the systemic side effects set in, they can last for 12 hours or more. Experts say these side effects should all resolve within 24 to 48 hours after your shot, though you may have some slight lingering fatigue or arm soreness after that.

Mullane says it’s not likely that your vaccine appointment time will directly correlate with when you experience peak symptoms in the following days. She says it’s best to avoid important events or taking on rigorous tasks the day after your vaccination if you’re concerned about the side effects.

“You may not want to get your vaccine the day before your important meeting,” Mullane says.

It’s OK to take an anti-inflammatory medication like Tylenol or ibuprofen if these post-vaccine symptoms are bothering you. But Mullane says it’s important not to take such medication before the shot, as it can interfere with your immune response. 

U.S. health officials are investigating six reports of a rare and serve blood clot called cerebral venous sinus thrombosis (CVST) among female recipients of the Johnson & Johnson COVID-19 vaccine. The blood clot prevents blood from draining out of the brain. Experts say that recipients of the Johnson & Johnson vaccine who develop any of these symptoms within three weeks of vaccination should seek care immediately:

  • Severe headache
  • Abdominal pain
  • Leg pain
  • Shortness of breath

After 48 Hours

Some mild side effects, like arm soreness and fatigue, can persist for a few days. If you continue to feel severe symptoms two full days after your vaccination, you should consider asking your doctor about next steps. It’s possible that while you were experiencing vaccine side effects, you were also ill with a COVID-19 or a different infection.

“If the symptoms persist beyond the 48 hours and aren't getting better, or if you develop any kind of respiratory symptoms, you should get evaluated,” Barron says.

It’s important to note that you cannot get COVID-19 from any of the approved vaccines. However, it can take up to two weeks after the second shot of the mRNA vaccines and after the single dose of the Johnson & Johnson vaccine to mount a full immune response. In the time before your vaccination or between your doses, you remain vulnerable to infection and the symptoms of the illness could coincide with your vaccine side effects.

What This Means For You

If you’re worried about how your body may respond to the vaccine, plan to take it easy in the day or two after your appointment. While it’s safe to exercise, go to work and be around other people during that time, side effects like fever and fatigue may make it uncomfortable to do so.

Side Effects Vary

When comparing your vaccine experience to others, remember that people’s side effects can vary greatly. Barron says that, in general, the side effects reported in the clinical trial data seems to align with how people have reacted to the vaccines in real-world distribution. 

“In the clinical trials, younger people were more likely to have reactions than older people,” Barron says. “They tended to have more of the systemic symptoms like the fever and chills and older people just reported a little bit of fatigue and arm soreness.”

“The healthy you healthier you are, the more in tune your immune system is, the higher the likelihood that you're going to have side effects because your immune system gets turned on,” Mullane adds.

If you don’t experience intense side effects, like a high fever or prolonged aches, it doesn’t necessarily mean your body won’t be protected against the virus. The time or intensity with which people’s immune systems respond to vaccines can differ based on many factors.

While the side effects can cause some pain and discomfort, Barron says that these effects are far preferable to the potential implications of getting sick with COVID-19.

“Forty-eight hours of side effects versus potentially the risk for hospitalization and death—I sort of think that favors the vaccine,” Barron says. “If there's any hesitation because of side effects, I’ll say the disease is far worse…or has the potential to be far worse.”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

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  1. Centers for Disease Control and Prevention. Possible side effects after getting a COVID-19 vaccine. Updated March 16, 2021.

  2. Centers for Disease Control and Prevention. Interim considerations: preparing for the potential management of anaphylaxis after COVID-19 vaccination. Updated March 3, 2021.

  3. Centers for Disease Control and Prevention. Local reactions, systemic reactions, adverse events, and serious adverse events: Pfizer-BioNTech COVID-19 vaccine. Updated December 13, 2020.