COVID-19 vaccine safety information

Updated November 2, 2022

Vaccine development usually takes years. However, in this case, scientists had already begun researching coronavirus vaccines during previous outbreaks like Severe Acute Respiratory Syndrome (SARS) in 2003, and Middle East Respiratory Syndrome (MERS) in 2012. SARS, MERS and COVID-19 are all members of the coronavirus family. Lessons learned from this earlier research provided a head start, allowing for rapid development of a COVID-19 vaccine. 

Get the latest news on the COVID-19 vaccines

Emergency use authorization

During an emergency, the FDA can issue an emergency use authorization (EUA) to provide more timely access to critical medical products like medicines and tests. 

The EUA process allows the FDA to authorize use based on less data than would be required for full approval, clearance or licensing. 

Once the EUA is given, it is in effect until the emergency ends, but it can always be revised or revoked as the emergency evolves, or more data becomes available. 

Vaccine ingredients 

Learn more about vaccine ingredients.

The vaccines do not include:

  • Fetal cells
  • Blood products, like red blood cells, white blood cells, plasma or platelets
  • COVID-19 virus cells
  • Mercury
  • Egg
  • Latex stoppers
  • Pork products
  • Graphene oxide
  • Microchips
    • Sometimes there are microchips on the outside of a syringe, so the health care professional can scan it quickly for digital records. The world's tiniest microchip is still much too big to insert into an immunization shot
  • Luciferase

mRNA technology 

Some of the COVID-19 vaccines, including the Pfizer and Moderna vaccines, use mRNA, or messenger RNA, to instruct your body to build the coronavirus’ spike protein. Once your body makes the spike protein, your immune system then produces antibodies to combat the coronavirus when it encounters it later. Learn more about mRNA vaccines.  

Adenovirus vector technology

The Johnson & Johnson vaccine is an adenovirus vector vaccine. (Adenovirus is the virus that causes the common cold. The virus in this vaccine has been changed so that it does NOT cause illness.) With this type of vaccine, a carrier, in this case adenovirus, acts as a delivery vehicle. The adenovirus has had the coronavirus spike protein added to its DNA. The adenovirus carries that genetic material into your body, delivering its modified DNA to your cells. Your cells will then make the spike protein, activating your immune system. Once activated, your immune system creates antibodies to fight off the spike protein. Learn more about the Johnson & Johnson vaccine

If you are pregnant or breastfeeding 

Both the American College of Obstetricians & Gynecologists and the Society for Maternal-Fetal Medicine recommend all pregnant people get one of the COVID-19 vaccines. 

The American College of Obstetricians & Gynecologists Practice Advisory states: “ACOG recommends that all eligible persons, including pregnant and lactating individuals, receive a COVID-19 vaccine or vaccine series.” 

The Society for Maternal-Fetal Medicine: “SMFM recommends that pregnant and lactating people be vaccinated against COVID19.”  

We encourage everyone who is pregnant or breastfeeding to get vaccinated against COVID-19.  

If you are immunocompromised 

We recommend immunocompromised people get the vaccine.  

If you have concerns, or a specific question related to your personal condition, we encourage you to speak with your doctor before getting the vaccine.   


Everyone 6 months and older is now eligible to get either a Pfizer or Moderna COVID-19 primary vaccine series. Everyone age 5 and older is able to get either the Pfizer or Moderna COVID-19 bivalent booster vaccine. 

Blood clots

Blood clots in the brain, abdomen and legs, along with low levels of platelets – the blood cells that help your body stop bleeding – have occurred in a small number of people who have received the Johnson & Johnson COVID-19 vaccine.  

Symptoms began approximately one to two weeks following vaccination. Most people who developed these problems were female, ages 18 to 49.  

This outcome is very rare. In a joint statement, the U.S. Food and Drug Administration (FDA) and the U.S. Centers for Disease Control and Prevention (CDC) stated, “The FDA has determined that the available data show that the vaccine’s known and potential benefits outweigh its known and potential risks in individuals 18 years of age and older.” 

 If you recently received the Johnson & Johnson vaccine, please contact your doctor if you develop any of the following symptoms within three weeks of receiving your vaccine:  

  • Shortness of breath 
  • Chest pain 
  • Leg swelling 
  • Persistent abdominal pain 
  • Severe persistent headaches 
  • Blurred vision 
  • Easy bruising or tiny blood spots under the skin beyond the injection site 

Heart inflammation

Myocarditis (inflammation of the heart) and pericarditis (inflammation of the lining outside the heart) have occurred in some people who received the mRNA COVID-19 vaccines. In most of these cases, symptoms began within a few days following receipt of the second dose of the vaccine. The chance of having this occur is very low.

You should seek medical attention right away if you have any of the following symptoms after receiving an mRNA COVID-19 vaccine:

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

We advise patients to take note of how your heart fees in the days after COVID-19 vaccination. If you experience any of these symptoms, please ask your doctor about it. If you have chest pain, call 911 or go to the emergency room. Learn more about myocarditis

Guillain-Barré syndrome

An extremely rare reaction may be linked to the Johnson & Johnson vaccine. About two weeks to six weeks after getting the Johnson & Johnson vaccine, some people experienced Guillain-Barré syndrome (GBS), a form of paralysis that’s generally reversible. This rare issue has mostly appeared in men over 50.

See your doctor if you have any of the following symptoms after receiving the Johnson & Johnson vaccine:

  • Weakness or tingling in your arms or legs
  • Double vision
  • Difficulty walking, speaking, chewing or swallowing
  • Bladder or bowel control problems

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