Are COVID-19 Vaccine Side Effects Contagious?

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 significantly reduces the risk of transmission.

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?

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

• Fatigue
• Fever and chills
• Headache
• Muscle pain
• Nausea
• Pain, redness, or swelling on the arm

You can expect to be watched for a longer period of time if you have a history of allergic reactions.

“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, told 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.”

Are Side Effects From COVID Vaccine Contagious?

COVID-19 vaccine side effects can feel like mild symptoms of an illness, but they do not mean that you're 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 said. “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, told Verywell that symptoms after vaccination do not represent infection. It's not the same as being infected with the virus.

You cannot spread the side effects of the vaccine you may feel to other people. So if you've been worried that the side effects from a COVID vaccine are contagious, you can rest easy.

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 this is 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 differently. And no one really knows why.

“It is unclear why some people get side effects and some don’t,” Juthani said. “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 already have 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 said. “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 said. “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 get 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 said. “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.”

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.