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What do we know about the ingredients used in the Pfizer-BioNTech and Moderna COVID-19 vaccines?

This article was published on
April 21, 2021

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Like other vaccines, COVID-19 vaccines contain an active ingredient that aims to teach the body how to recognize the virus, so that the defend itself when exposed. There are multiple ingredients in vaccines in addition to the active ingredient. The Pfizer-BioNTech and Moderna COVID-19 vaccines both use mRNA as the active ingredient and also contain ingredients like potassium chloride, monobasic potassium, phosphate, sodium chloride, dibasic sodium phosphate, and sucrose. Potassium, chloride, and phosphate are minerals that are commonly found in foods and medications. Sodium chloride is another name for salt, and sucrose is a type of sugar. All of these ingredients are commonly used in vaccines to deliver the medication as a liquid solution, and to maintain stability and pH levels. Unlike other vaccines, mRNA vaccines use very small fats (lipid nanoparticles) to deliver the mRNA into your body. Once in the body, these fats protect the mRNA, so that the mRNA can make it to cells, where it helps the body develop immunity. Once the mRNA is delivered to the cells, the lipids dissolve and are removed from the body. One part of the lipid nanoparticle is something called polyethylene glycol (PEG), an ingredient used in many toothpastes, shampoos, and other products as a thickener, moisture carrier, and solvent. PEG is also used in medications, including as laxatives, and in biopharmaceutical products. PEG has occasionally resulted in severe allergic reactions in some people. PEG has not been used in an approved vaccine before. Some scientists have suggested that PEG could be the reason for the allergy-like reactions that a small number of people have had following COVID-19 vaccination. However, this speculation has not been confirmed, and there remains considerable debate about whether or not PEG may have caused these reactions. The US National Institute of Allergy and Infectious Diseases is currently working with the US Food and Drug Administration to study how people respond to the mRNA vaccines when they have a history of allergic reactions or have high levels of antibodies against PEG. Severe reactions to vaccines can happen, but reactions to the mRNA COVID-19 vaccines have been rare (as of February 2021). In general, vaccination is both recommended and safe for most people.

Like other vaccines, COVID-19 vaccines contain an active ingredient that aims to teach the body how to recognize the virus, so that the defend itself when exposed. There are multiple ingredients in vaccines in addition to the active ingredient. The Pfizer-BioNTech and Moderna COVID-19 vaccines both use mRNA as the active ingredient and also contain ingredients like potassium chloride, monobasic potassium, phosphate, sodium chloride, dibasic sodium phosphate, and sucrose. Potassium, chloride, and phosphate are minerals that are commonly found in foods and medications. Sodium chloride is another name for salt, and sucrose is a type of sugar. All of these ingredients are commonly used in vaccines to deliver the medication as a liquid solution, and to maintain stability and pH levels. Unlike other vaccines, mRNA vaccines use very small fats (lipid nanoparticles) to deliver the mRNA into your body. Once in the body, these fats protect the mRNA, so that the mRNA can make it to cells, where it helps the body develop immunity. Once the mRNA is delivered to the cells, the lipids dissolve and are removed from the body. One part of the lipid nanoparticle is something called polyethylene glycol (PEG), an ingredient used in many toothpastes, shampoos, and other products as a thickener, moisture carrier, and solvent. PEG is also used in medications, including as laxatives, and in biopharmaceutical products. PEG has occasionally resulted in severe allergic reactions in some people. PEG has not been used in an approved vaccine before. Some scientists have suggested that PEG could be the reason for the allergy-like reactions that a small number of people have had following COVID-19 vaccination. However, this speculation has not been confirmed, and there remains considerable debate about whether or not PEG may have caused these reactions. The US National Institute of Allergy and Infectious Diseases is currently working with the US Food and Drug Administration to study how people respond to the mRNA vaccines when they have a history of allergic reactions or have high levels of antibodies against PEG. Severe reactions to vaccines can happen, but reactions to the mRNA COVID-19 vaccines have been rare (as of February 2021). In general, vaccination is both recommended and safe for most people.

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What our experts say

Like other vaccines, COVID-19 vaccines contain an active ingredient that aims to teach the body how to recognize the virus, so that the defend itself when exposed.

There are multiple ingredients in vaccines in addition to the active ingredient. The Pfizer-BioNTech and Moderna COVID-19 vaccines both use mRNA as the active ingredient and also contain ingredients like potassium chloride, monobasic potassium, phosphate, sodium chloride, dibasic sodium phosphate, and sucrose.

Potassium, chloride, and phosphate are minerals that are commonly found in foods and medications. Sodium chloride is another name for salt, and sucrose is a type of sugar. All of these ingredients are commonly used in vaccines to deliver the medication as a liquid solution, and to maintain stability and pH levels.

Unlike other vaccines, mRNA vaccines use very small fats (lipid nanoparticles) to deliver the mRNA into your body. Once in the body, these fats protect the mRNA, so that the mRNA can make it to cells, where it helps the body develop immunity. Once the mRNA is delivered to the cells, the lipids dissolve and are removed from the body.

One part of the lipid nanoparticle is something called polyethylene glycol (PEG), an ingredient used in many toothpastes, shampoos, and other products as a thickener, moisture carrier, and solvent. PEG is also used in medications, including as laxatives, and in biopharmaceutical products. PEG has occasionally resulted in severe allergic reactions in some people.

PEG has not been used in an approved vaccine before. Some scientists have suggested that PEG could be the reason for the allergy-like reactions that a small number of people have had following COVID-19 vaccination. However, this speculation has not been confirmed, and there remains considerable debate about whether or not PEG may have caused these reactions.

The US National Institute of Allergy and Infectious Diseases is currently working with the US Food and Drug Administration to study how people respond to the mRNA vaccines when they have a history of allergic reactions or have high levels of antibodies against PEG. Severe reactions to vaccines can happen, but reactions to the mRNA COVID-19 vaccines have been rare (as of February 2021). In general, vaccination is both recommended and safe for most people.

Context and background

New vaccines to prevent COVID-19 infection have been approved by regulatory authorities in the US, Europe, and other regions. The first two vaccines to receive temporary authorization in the US and EU are both mRNA vaccines that have used new technology to create immunity in the body. Recently, questions have arisen about the ingredients used in the new COVID-19 vaccines. The ingredient details of the Pfizer-BioNTech and the Moderna COVID-19 vaccines are detailed below.

According to the US Food and Drug Administration Fact Sheet for the Pfizer-BioNTech COVID-19 vaccine, the full list of ingredients includes the following: mRNA, lipids ((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, and cholesterol), potassium chloride, monobasic potassium phosphate, sodium chloride, dibasic sodium phosphate dihydrate, and sucrose. 

According to the US Food and Drug Administration Fact Sheet for the Moderna COVID-19 vaccine, the full list of ingredients includes the following: messenger ribonucleic acid (mRNA), lipids (SM-102, polyethylene glycol [PEG] 2000 dimyristoyl glycerol [DMG], cholesterol, and 1,2-distearoyl-sn-glycero-3-phosphocholine [DSPC]), tromethamine, tromethamine hydrochloride, acetic acid, sodium acetate, and sucrose.

Resources

  1. Vaccine to Prevent Coronavirus Disease 2019 (COVID-19) in Individuals 16 Years of Age and Older (US FDA)
  2. Fact Sheet for Recipients and Caregivers, Emergency Use Authorization of the Moderna COVID-19 Vaccine to Prevent Coronavirus Disease 2019 (COVID-19) in Individuals 18 Years of Age and Older (US FDA)
  3. Vaccine Knowledge Project (University of Oxford)
  4. COVID-19 Vaccines (University of Oxford)
  5. Suspicions grow that nanoparticles in Pfizer’s COVID-19 vaccine trigger rare allergic reactions   (ScienceMag)
  6. Vaccine Ingredients: Frequently Asked Questions (AAP)

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