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Are COVID-19 vaccine ingredients safe?

A healthcare provider prepares to give a man a shot.

COVID-19 vaccines give us our best shot at beating the pandemic. In time, everyone will have a chance to get one.

But in the meantime, if you have concerns about what's in them, these facts may give you peace of mind.

No live virus in the vaccine

Vaccines contain ingredients that help your body build immunity against a specific virus. However, not all vaccines have the same ingredients.

The two COVID-19 vaccines currently authorized for use in the U.S. are the Pfizer-BioNTech and Moderna vaccines. They are a newer type of vaccine, called mRNA vaccines, the Centers for Disease Control and Prevention (CDC) reports.

They don't use live or weakened viruses to build immunity. Instead, they use messenger RNA (mRNA). The mRNA instructs cells to make a harmless piece of the virus's genetic material called the spike protein, which is found on the surface of the coronavirus. This teaches the immune system to recognize and fight the real virus. But because the vaccine doesn't contain any live virus, there's no way it can give you COVID-19.

The vaccine's mRNA does not stay in the body, and it cannot change your DNA.

Also not included

The Pfizer and Moderna vaccines also lack some other ingredients some people may be concerned about. They do not have:

  • Preservatives, such as thimerosal (which contains an organic form of mercury). Most vaccines do not use thimerosal or mercury. And the type of mercury found in the few vaccines that do have thimerosal is not likely to build up in the body. In tiny amounts, it is safe in vaccines. Learn more about vaccine safety.
  • Formaldehyde, used to help make some vaccines.
  • Eggs, latex or antibiotics. Some people are allergic to these things.
  • Microchips. Scientists are not putting microchips in the vaccines to track us. That's a myth. In fact, it's not even possible to do so.

What is in the shot?

Like all vaccine ingredients, those in the COVID-19 vaccine serve a specific purpose. For instance, some ingredients help the vaccine work. Others are needed to help produce the vaccine.

Here are some of the other ingredients in the two COVID-19 vaccines now in use. Ask your doctor if you have any concerns about them.

Pfizer-BioNTech vaccine:

  • ((4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate).
  • 2[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide.
  • 1,2-Distearoyl-sn-glycero-3-phosphocholine.
  • Cholesterol.
  • Potassium chloride.
  • Monobasic potassium phosphate.
  • Salt.
  • Dibasic sodium phosphate dihydrate.
  • Sugar.

Moderna vaccine:

  • SM-102.
  • Polyethylene glycol (PEG) 2000 dimyristoyl glycerol (DMG).
  • Cholesterol.
  • 1,2-distearoyl-sn-glycero-3-phosphocholine.
  • Tromethamine.
  • Tromethamine hydrochloride.
  • Acetic acid.
  • Sodium acetate.
  • Sugar.

Talk to your doctor

Some side effects have occurred with COVID-19 vaccines. Most are minor, like a sore arm. A few people have had more serious allergic reactions, but this is very rare. CDC says that if you have had an allergic reaction to PEG or polysorbate, you should not get an mRNA COVID-19 vaccine. You can help make your shot even safer by telling your provider if you:

  • Have any allergies or other health problems.
  • Have ever had an allergic reaction to a vaccine.

To learn more about the COVID-19 vaccines, visit our Coronavirus health topic center.

Reviewed 2/15/2021

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