vaccine

How Long Do COVID Vaccine Side Effects Last?

Here's a breakdown of the potential side effects and what you need to know

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As many receive their first or possibly second dose of the coronavirus vaccine, some may be experiencing side effects, but at what point should you seek medical attention?

Here's a breakdown of the potential side effects and what you need to know.

What are the potential side effects?

Side effects are possible after receiving any COVID vaccine currently being administered in the U.S.

Experiencing side effects isn't necessarily a bad thing. In fact, it's a sign your body is responding and the vaccine is working.

According to Pfizer, about 3.8% of their clinical trial participants experienced fatigue as a side effect and 2% got a headache. 

Moderna says 9.7% of their participants felt fatigued and 4.5% got a headache.

The CDC reports the most common side effects for the vaccines is at the injection site. They include:

  • Pain
  • Redness
  • Swelling

Common side effects in the body include:

  • Tiredness
  • Headache
  • Muscle pain
  • Chills
  • Fever
  • Nausea

The Centers for Disease Control and Prevention advises people to stick around for 15 minutes after vaccination, and those with a history of other allergies for 30 minutes, so they can be monitored and treated immediately if they have a reaction.

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As the nation gets ready to start receiving vaccinations for COVID-19, it's important to understand the side effects. Here is what doctors are saying people can expect.

At what point should you call a doctor?

In most cases, discomfort from pain or fever is a normal sign that your body is building protection, the CDC states. Still, the agency recommends you contact your doctor or healthcare provider if:

  • The redness or tenderness where you got the shot gets worse after 24 hours
  • Your side effects are worrying you or do not seem to be going away after a few days

Anyone who believes they are experiencing a severe allergic reaction after leaving the vaccination site should also seek immediate medical care by calling 911, the CDC recommends.

When do the side effects start and how long do they last?

According to the CDC, side effects usually start within a day or two of getting the vaccine, but they should also go away "in a few days."

Are side effects more likely after the first or second dose?

With the two-shot vaccines, people are more likely to report side effects after their second dose, experts have said.

According to the CDC, side effects after your second shot "may be more intense than the ones you experienced after your first shot." 

"These side effects are normal signs that your body is building protection and should go away within a few days," the CDC states.

In trials of both the Moderna and Pfizer vaccines, more people experienced side effects after the second dose.

But that doesn't mean that you shouldn't get your second shot if you get side effects after your first, experts say.

The CDC also noted that both shots are needed.

"The Pfizer-BioNTech COVID-19 Vaccine and Moderna COVID-19 Vaccine both need 2 shots in order to get the most protection," the CDC states. "You should get the second shot even if you have side effects after the first shot, unless a vaccination provider or your doctor tells you not to get it."

The coronavirus vaccine has been shown to be safe, but some of the temporary side effects can feel pretty rough — especially when you get that second dose. Iahn Gonsenhauser, chief patient safety officer at the Ohio State University Wexner Medical Center, described his own experience with “extreme” fever and chills after his second shot so you know what to expect.

Are certain people more likely to experience side effects?

There are also some factors that could make you more likely to experience side effects.

Experts say younger people are more likely to experience side effects because they have more robust immune systems.

Women are much more likely to report side effects than men. Some of this may be because they may just be better reporters, but it could be more than just that.

Why is that?

Estrogen can elevate immune responses, while testosterone can decrease it. Many immune modulating genes also live on an "x" chromosome, which women have two of, while men have one.

Data from the CDC also reported women were more likely to experience side effects than men, according monitoring from the first month of vaccinations.

From Dec. 14 through Jan. 13, more than 79% of side effects were reported by women, the data showed. Meanwhile, women received roughly 61.2% of the doses administered during that same time.

While many are posting questions and concerns about coronavirus vaccine side effects, it's important to remember that many people have no side effects from vaccines at all, NBC News' Dr. Natalie Azar explains.

Does Experiencing Side Effects Mean You Had COVID?

Side effects could also vary depending on whether or not you've had coronavirus.

If you had COVID a while ago or you have some immunity already, the vaccine can act like a booster, which in some cases can be completely asymptomatic.

But not getting side effects isn't a negative, health experts say. It simply means your body didn't react with as much of an inflammatory response.

What can you do if you experience side effects?

The CDC recommends people talk to their doctors about taking over-the-counter medicines like ibuprofen, acetaminophen, aspirin, or antihistamines, for any pain and discomfort after getting vaccinated. 

"You can take these medications to relieve post-vaccination side effects if you have no other medical reasons that prevent you from taking these medications normally," the CDC states. "It is not recommended you take these medicines before vaccination for the purpose of trying to prevent side effects."

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