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COVID-19 vaccine side effects: What to expect when you receive an mRNA coronavirus vaccine
General Wellness

COVID-19 vaccine side effects: What to expect when you receive an mRNA coronavirus vaccine

By Your Health staff
Posted: February 12, 2021

The COVID-19 vaccine will help protect you from getting the novel coronavirus. The Pfizer and Moderna vaccines are both administered in two doses — 21 days apart for Pfizer and 28 days apart for Moderna.

Have questions about the COVID-19 vaccine?

We know you may have many questions about the vaccine, the distribution plan and what it means for you and your loved ones, so we’ve identified several of the most frequently asked questions to address here.


After each dose of the COVID-19 vaccine, you might experience certain symptoms, commonly referred to as side effects, that can occur after receiving an immunization. These symptoms are “reactogenic effects”. They are a sign that your body is building protection against the virus.

What should you expect?

The most commonly reported reactogenic symptoms are:

  • Pain in the arm where you got the shot
  • Fatigue; your body feeling tired/run down
  • Headache
  • Body aches
  • Fever and/or chills

Reports of symptoms are higher after the second dose. If you have previously had the coronavirus, you may experience a higher rate of these symptoms after the first dose compared to someone who has not previously had the virus.

Each person’s reaction to the shot is different. Some people may experience all of the above-mentioned symptoms and may feel as though they have the flu or a severe cold. Others may not have any symptoms.

Tips for dealing with reactogenic effects

To help reduce pain or discomfort in the arm where you received the shot, you can:

Apply a clean, cool, wet washcloth on the injection site
Use or exercise your arm to help “work out” soreness or stiffness
To help reduce discomfort from fever, you can:

  • Drink plenty of fluids to keep your body hydrated
  • Dress lightly

Over-the-counter medications, like ibuprofen or acetaminophen, can be used as a pain reliever or fever reducer, but are primarily recommended after you receive the vaccine and if you experience symptoms that cannot be managed without medications.

If you do have symptoms, they should go away within a couple days.


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Why do reactogenic effects happen?

Because our body sees the protein that is created as a result of the mRNA vaccine as foreign, it builds an immune response that consumes a great deal of energy within our bodies. This may result in a person feeling tired/run down — or for their body to ache for a short period of time. 

Have there been any severe reactions to the vaccine?

No serious adverse side effects have been definitively associated with the COVID-19 vaccines.  

While there were several individuals in the clinical trials who developed a mild, temporary inability to move facial muscles, patients on both sides — those who received the vaccine and those who received the placebo — reported this and the FDA has not concluded that the vaccination caused this to occur.   Other reports have emerged since the vaccine has been being administered nationwide, but at this time the FDA has again been unable to link any severe reactions directly to the vaccine. 

What about allergic reactions?

There is a small risk of anaphylactic reaction, as with any vaccine. Thus far, the CDC has reported the rate of anaphylaxis among Americans immunized following the Pfizer vaccine is 0.001% and 0.0002% following the Moderna vaccine. 

If a person has had a previous severe, anaphylactic reaction to a vaccine in the past, they should discuss with their doctor about reviewing the COVID-19 vaccine.

However, severe allergies to medications that are not vaccines do not mean a person cannot receive the COVID-19 vaccination. There is also no latex included in the vaccine packaging, so people with latex allergies are able to receive the COVID-19 vaccines.

The CDC does recommend that people with a history of an immediate allergic reaction of any severity to a vaccine or an injectable drug — or a person with a history of anaphylaxis to any substance — should be observed for 30 minutes after receiving the COVID-19 vaccine.

Still Have Questions About The COVID-19 Vaccine?

We've put together a guide to answer the most frequently asked questions about the Pfizer and Moderna vaccines.

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