COVID-19 Vaccine Side Effects in 2023: What to Expect

With updated COVID-19 vaccines from Pfizer, Moderna, or Novavax rolling out this fall, many people who are planning to get the shot are wondering if they’ll have side effects.

According to the Centers for Disease Control and Prevention (CDC), any vaccine can cause mild side effects, and they usually go away within a few days of getting a shot.

Stuart Ray, MD, an infectious disease specialist and a professor of medicine at Johns Hopkins University School of Medicine, told Verywell that some side effects come on right when you get a vaccine while others might show up later in the day or the next day.

A common example? Having a sore arm after you get your annual flu shot.

Here’s what we know about COVID vaccine side effects in 2023, including what experts say you can do to minimize any side effects that you may have.

What Are the Side Effects of the Latest COVID Vaccine?

Hannah Newman, MPH, senior director of infection prevention at Northwell Lenox Hill Hospital in New York, told Verywell that common side effects of the updated COVID vaccine are similar to ones that people had with previous versions.

Possible side effects from COVID vaccines in 2023 include:

• A sore arm 
• Pain, swelling, or redness at the injection site
• Tiredness
• Headache
• Muscle pain or aches
• Feeling under the weather
• Fatigue 
• Nausea
• Chills
• Fever 

Ray explained that since a COVID vaccine is injected into a muscle in your arm (specifically, the deltoid muscle), it’s not unusual to feel a little pain. However, “holding still during the injection, and then for the next few hours actively using that muscle,” can help minimize the discomfort.

It’s not as common as arm pain, but Ray said that some people may have a general feeling of being unwell (malaise), redness and swelling in their arm where the needle went in, or more muscle soreness after a COVID shot. Side effects like fever, chills, headaches, or noticeable swelling of lymph nodes around the arm (like in the armpit) are even less common.

How Long Do COVID Vaccine Side Effects Last?

According to Ray, side effects like arm discomfort come on when you get the shot and don’t last very long. Muscle soreness, stiffness, or malaise may come on a few hours after you get the vaccine, and won’t last more than a few days.

It’s rare, but Ray said that more serious reactions to a vaccine (like anaphylaxis, a life-threatening allergic reaction) can come on immediately after getting the shot or may not show up for a day or so after.

Newman said that if you have side effects, they’ll most likely be mild. How long COVID vaccine side effects last can vary, lasting only a few hours to a couple of days. And some people don’t have COVID vaccine side effects at all.

Why Do Some People Have No Side Effects?

According to Newman, everyone’s immune system responds differently to different vaccines, and that can influence whether or not they have side effects.

Ray said that some people who react to vaccines may have more reactive immune systems, possibly because there are genetic and environmental factors at play. However, more research is needed to understand why some people have side effects after vaccines and others don’t.

“There is some evidence for higher immune responses in people with more side effects, but this relationship is not super strong,” said Ray. “People who experience few side effects from the COVID-19 vaccine tend to have excellent immune responses, so it’s just an interesting trend worthy of deeper understanding.”

If you do have side effects after getting a vaccine, Newman said it means that your immune system is working and building a response. However, “even if you don’t experience side effects, your body is still building protection.”

Will You Have Side Effects to the New Shot If You Didn’t Have Side Effects Last Time?

Ray said that individual immune responses and differences in the formulation of the newest COVID vaccine could explain why some people may get side effects this time around even if they didn’t have side effects when they got vaccinated before.

“The reaction to a vaccine is a complex combination of the person’s own immune system plus other factors including precise formulation of the vaccine,” said Ray. “We do not completely understand this complex mixture of factors, but people tend to have similar reactions to a series of vaccinations.”

Do Some COVID Shot Brands Cause More Side Effects Than Others?

According to Ray, since COVID vaccine formulations vary a little from brand to brand, there could be minor differences in side effects.

For example, Ray said that Pfizer and Moderna COVID shots are mRNA vaccines that tend to be “very effective and also relatively reactogenic,” meaning that they may cause more side effects than other, less effective vaccines,

However, Ray added that the shots are still more or less considered equal as long as these differences are not major—that is, all the shots offer protection and are safe.

Newman said that all three of the currently available vaccine brands—Pfizer, Moderna, and Novavax—have had similar side effects reported: injection site tenderness, fatigue, headache, and muscle pain.

Novavax seems to have a lower risk of causing more serious side effects like inflammation of the heart muscle (myocarditis) or swelling of the membrane around the around (pericarditis), but Newman said that the risk is not zero.

“This is a rare side effect that can occasionally occur, especially in young men,” said Newman, adding that there is also a risk of these conditions “after infection with the COVID-19 virus as well.”

Ray said that the immune response to the Novavax COVID vaccine compares to the one stimulated by mRNA vaccines, and there might be fewer side effects. However, “we can’t be too sure about these comparisons because we don’t have a large head-to-head comparison in the same population.”

Will Getting a Flu, RSV, and COVID Shot on the Same Day Cause More Side Effects?

Newman said that getting a COVID shot, flu vaccine, and/or the RSV vaccine on the same day should not raise your risk of having more side effects.

“There has not been an association of more side effects or more severe side effects when multiple vaccines are given at one time,” said Ray.

Getting more than one vaccine on the same day doesn’t seem to be any worse overall than getting them on separate days. However, Ray said that if you plan to get them all at once, try to remember where you got each injection.

“It’s worth remembering where you got each injection so that if you have an intense local reaction to one of them, you’ll have a better chance of knowing which one it was,” said Ray, though it’s still “not likely” you’ll have any problem.

How to Reduce COVID Vaccine Side Effects

Suellen Hopfer, PhD, associate professor of Health, Society & Behavior at the University of California, Irvine, told Verywell there are a few things you can do to help with COVID vaccine side effects. Here are some general tips to keep in mind:

• Apply a cool compress (like an ice pack or a cool, damp cloth) to your arm to relieve pain, swelling, or redness.
• Stay physically active, and that includes moving and using the arm where you got the shot.
• Stay well-hydrated, especially for the first 1-2 days after you get vaccinated.
• Get plenty of rest.
• If needed or if your provider suggests it, take over-the-counter anti-inflammatory medications.

To try to prevent side effects, Hopfer recommends getting a good night’s sleep the night before and getting your shot in the morning if you can, which studies have suggested may “enhance the immune response” and possibly lead to fewer side effects.”

And remember, if your side effects are getting worse or not getting better within a few days, call your provider.

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.