What are the vaccines’ side effects?

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Mayo Clinic

By Mayo Clinic Staff

COVID-19 vaccines can cause mild side effects after the first or second dose, including:

  • Pain, redness or swelling where the shot was given
  • Fever
  • Fatigue
  • Headache
  • Muscle pain
  • Chills
  • Joint pain
  • Nausea and vomiting
  • Swollen lymph nodes
  • Feeling unwell

Most side effects go away in a few days.

In the U.S., there has been an increase in reported cases of myocarditis and pericarditis after mRNA COVID-19 vaccination, particularly in males ages 12 through 29. Myocarditis is the inflammation of the heart muscle, while pericarditis is the inflammation of the lining outside the heart. These reports are rare.

Of the cases reported, the problem happened more often after the second dose of the COVID-19 vaccine and typically within one week after COVID-19 vaccination. Most of the people who received care felt better after receiving medicine and resting. Symptoms to watch for include:

  • Chest pain
  • Shortness of breath
  • Feelings of having a fast-beating, fluttering or pounding heart

If you or your child develops myocarditis or pericarditis after a dose of an mRNA COVID-19 vaccine, the CDC recommends avoiding getting another dose of any COVID-19 vaccine.

The Janssen/Johnson & Johnson COVID-19 vaccine can cause thrombosis with thrombocytopenia syndrome. This is a blood-clotting problem that can be life-threatening.

As a result, the FDA is restricting use of the Janssen/Johnson & Johnson vaccine to certain people age 18 and older. Examples include people who had a severe allergic reaction after getting an mRNA COVID-19 vaccine and people who can’t get an mRNA COVID-19 vaccine due to limited access or personal or religious concerns. Research suggests there isn’t an increased risk of this blood-clotting problem after mRNA COVID-19 vaccination.

Serious side effects of the Janssen/Johnson & Johnson COVID-19 vaccine can occur within three weeks of vaccination and require emergency care. Possible symptoms include:

  • Shortness of breath
  • Persistent stomach pain
  • Severe or persistent headaches or blurred vision
  • Chest pain
  • Leg swelling
  • Easy bruising or tiny red spots on the skin beyond the injection site

This vaccine shouldn’t be given to anyone who develops thrombosis with thrombocytopenia after getting the Janssen/Johnson & Johnson COVID-19 vaccine or any other adenovirus vector COVID-19 vaccine.

Mild to moderate headaches and muscle aches are common in the first three days after vaccination and don’t require emergency care.

Some people who received the Janssen/Johnson & Johnson COVID-19 vaccine have developed Guillain-Barre syndrome. The chances of this happening are very low. This disorder is most often reported within 42 days after vaccination, mostly in men. Many of the men are ages 50 to 64. Seek immediate medical care if you have weakness or tingling sensations, difficulty walking, difficulty with facial movements, double vision, and difficulty with bladder control.