Are COVID-19 Vaccine Side Effects Contagious?

Illustration of 3 people in pain with an "x" on their arm, like where they got a vaccine.


Key Takeaways

  • Side effects from a COVID-19 vaccine do not indicate an infection or contagiousness.
  • If you experience side effects after getting a COVID-19 vaccine, it does not mean that you have the virus or that you could spread it to others.
  • However, if you experience symptoms for longer than 72 hours after you get the shot, you might want to get a COVID-19 test. It's possible that you were infected with the virus around the same time that you were vaccinated or between doses.

Being fully vaccinated against COVID-19 keeps you from becoming infected and helps you avoid severe illness if you do get sick. Studies have also shown that getting vaccinated reduces the risk of transmission significantly.

However, some people are still worried about getting sick and spreading the virus after getting the shot, and there is confusion about what it means if you have (or do not have) side effects from the vaccine. Is your post-vaccine fever contagious?

Here's how to tell the difference between COVID vaccine side effects and signs or symptoms of a COVID infection.

What Are the COVID-19 Vaccine Side Effects?

According to the Centers for Disease Control and Prevention (CDC), there are several side effects of the COVID-19 vaccines that are relatively common. If you experience these side effects they are usually not serious and go away on their own in a short time:

Severe reactions to the COVID vaccine usually occur within 15 minutes of getting the shot. That's why most vaccination sites ask you to stick around for 15 minutes to a half-hour after you get your dose to monitor you.

“If you’ve had a history of anaphylaxis, you should be observed for 30 minutes to make sure that you don’t develop another such episode,” Manisha Juthani, MD, infectious diseases specialist at Yale Medicine and associate professor at the Yale School of Medicine, tells Verywell. “For symptoms that develop after the initial vaccination period, if you have symptoms that last more than 72 hours after your vaccine, you should call your doctor. If you develop a rash at the site of the vaccination, you could have a local allergic reaction.”

Can I Spread Vaccine Side Effects to Other People?

COVID-19 vaccine side effects can feel like mild symptoms of an illness, but they do not mean that you are sick. The signs and symptoms that you might experience—like a fever and body aches—are not contagious.

“Side effect symptoms cannot be spread to others,” Juthani says. “The vaccine cannot give you the virus, so the symptoms you experience are a manifestation of your immune system building a response so that you can fight the virus in the future should you be exposed to it.”

Amber D’Souza, PhD, professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health, tells Verywell that symptoms after vaccination do not represent infection, which means it's not the same as being infected with the virus. Therefore, you cannot spread the side effects of the vaccine to other people.

"You cannot get infected with coronavirus from the vaccine. It does not include the entire coronavirus sequence," D'Souza says. That means that you cannot get the SARS-CoV-2 virus from the vaccine or spread the virus unknowingly to other people.

What If I Don’t Have Any Side Effects? 

The common side effects of the vaccine are all signs that your body is building protection against the SARS-CoV-2 virus. However, some people do not experience any symptoms after they get the shot—and that's OK.

If you don't experience any side effects from the COVID-19 vaccine, it does not mean that your body is not responding. Everyone's immune system works a little bit differently—and we're not sure why.

“It is unclear why some people and side effects and some don’t,” Juthani says. “From the vaccine studies, whether you got side effects or not, people were still protected. Count yourself as lucky if you don’t get side effects.”

Will My Vaccine Side Effects Be Worse If I've Had COVID?

Side effects from the second shot are sometimes more intense than the first. However, people who have already had COVID-19 might experience more significant side effects even after their first dose of the vaccine.

“In a way, this is a good sign that your body is recognizing the fragment of the virus and mounting an immune response to fight it,” Juthani says. “The immunity developed from the vaccine is much stronger than immunity from natural infection, so it is still worth getting vaccinated.”

My Side Effects Are Not Going Away—Could I Have COVID?

In some cases, you might get your COVID-19 shot around the same time that you have been exposed to the virus. If this happens, you could develop symptoms of COVID-19—in which case you would be capable of spreading it to others.

“Some people by chance may become infected with coronavirus between their first and second dose before they are fully immune,” D’Souza says. “It takes several days after infection for symptoms to develop so they might get [it before] their second dose.”

Common side effects of the vaccine, like fatigue, fever, or body aches, can also occur if you have a COVID-19 infection. The way to tell the difference is by the timing and severity of your symptoms. If you don't start to feel better within a few days of getting your shot, or your side effects are getting worse, you should get tested for COVID-19.

“If your symptoms last longer than 72 hours, it is worth making sure you don’t actually have COVID-19,” Juthani says. “If you do, you didn’t get it from the vaccine, you just happened to get it from someone else around the time you got your vaccine.”

What This Means For You

You cannot get infected with the SARS-CoV-2 virus from a COVID-19 vaccine. The side effects that you might experience are just a sign that your body's immune system is responding.

However, if your side effects—like fever and body aches—do not get better within 72 hours of getting your shot, or they get worse, you should get tested for COVID-19. It's possible that you caught the virus around the same time that you got your shot or in between doses.

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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Article Sources
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  1. Centers of Disease Control and Prevention (CDC). Benefits of Getting a COVID-19 Vaccine. Updated April 12, 2021.

  2. Nature. COVID research updates: One vaccine dose can nearly halve transmission risk. Updated April 30, 2021.

  3. Centers for Disease Control and Prevention (CDC). Possible Side Effects After Getting a COVID-19 Vaccine. Updated March 16, 2021.

  4. Centers for Disease Control and Prevention (CDC). COVID-19 Vaccines and Severe Allergic Reactions. Updated March 4, 2021.