After the Vaccine: What to Expect

Vaccine side effects

What side effects might I expect after the COVID-19 vaccine?

Side effects that have been reported following COVID-19 vaccination include:

  • Injection site pain, swelling, or redness
  • Arm rash ("COVID arm")
  • Tiredness
  • Headache
  • Muscle or joint pain
  • Fever or chills
  • Nausea or vomiting
  • Swollen lymph nodes
  • Generally feeling unwell

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Side effects are more commonly reported after the 2nd dose of the vaccine and are more common in those under 55 years of age. These side effects are usually mild to moderate, but in rare cases can be more severe. Studies of the vaccines are ongoing, so other side effects are possible.  

What serious adverse events should I be aware of?

There is a small chance that the vaccine could cause a severe allergic reaction, usually occurring within a few minutes to an hour after vaccine administration. Signs could include difficulty breathing, swelling of your face or throat a fast heartbeat, a rash, and dizziness or weakness. Studies of the vaccines are still ongoing, so other serious and unexpected side effects may occur.

Arm rash following Moderna vaccination

Annoying but harmless, experts say

About the rash

  • Some recipients of the Moderna COVID-19 vaccine have reported a rash that showed up days after they got their shots.

Expert advice

  • Physicians say the reaction (now called “COVID arm”) is harmless, causing itchiness or aching at worst, and goes away on its own.
  • Individuals who have the rash are encouraged to receive their second dose of Moderna to become fully vaccinated.
  • Those who experienced the rash after their first vaccine should tell their vaccination provider that they experienced a rash or “COVID arm” after the first shot. The vaccination provider may recommend getting the second shot in the opposite arm.

Rash details

  • The rash is red, raised, sometimes itchy or tender to the touch, and appears almost always on the arm where the vaccine was given.
  • The rash appears to be more common in women than men, and is more frequently seen in those under 60.
  • It typically occurs between 4 and 11 days after being vaccinated, and goes away on its own 2 to 11 days after onset.


  • Many people find the rash, though annoying, just goes away by itself without any additional care.
  • For those who feel they need help to sooth itching or irritation, ice at the site of the rash may be effective. Drinking plenty of water and stretching the arm are also recommended.
  • If the rash is itchy, you can take an antihistamine. If it is painful, you can take a pain medication like acetaminophen or a non-steroidal anti-inflammatory drug (NSAID).

Reporting the rash

  • Researchers encourage those who experience the reaction to report it on the Centers for Disease Control and Prevention’s vaccine adverse reaction system, known as V-safe.
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What should I do if experience an adverse reaction?

If you experience a severe allergic reaction (difficulty breathing, swelling of your face or throat, a fast heartbeat, dizziness, or weakness), call 911 or go to the nearest hospital.

If you have other side effects that bother you or do not go away, call your healthcare provider. 

Please note: If you have insurance, your insurance will be billed for the vaccine and you will receive an Explanation of Benefits (EOB). For Medicare Advantage patients, traditional Medicare will be billed.

v-safeSign-up with v-safe. V-safe is a smartphone-based tool that uses text messaging and web surveys to provide personalized health check-ins after you receive a COVID-19 vaccination. Through v-safe, you can quickly tell CDC if you have any side effects after getting the COVID-19 vaccine. Depending on your answers, someone from CDC may call to check on you and get more information. And v-safe will remind you to get your second COVID-19 vaccine dose if you need one.

Your participation in CDC’s v–safe makes a difference — it helps keep COVID-19 vaccines safe.

Please use the link below for information on how to register using your smartphone.