Answering "What's in the Vaccine?"

Is that even a word?

There are currently three COVID‑19 vaccines authorized for use in the United States (information on EUAs can be found in my earlier post, "COVID‑19 Vaccine Q&A"). They all have different ingredients, and many of those ingredients are nearly impossible to pronounce. The goal of this post is to provide you with the list of ingredients in each vaccine and to explain why those ingredients are present.

Pfizer-BioNTech COVID‑19 Vaccine

Authorized for use on December 11, 2020, the Pfizer-BioNTech COVID‑19 vaccine consists of strands of messenger RNA (genetic instructions) coated in lipid nanoparticles (tiny blobs of fat) that temporarily teach some of your cells how to make a substance that is nearly identical to bumps found on the surface of the virus that causes COVID‑19 (SARS‑CoV‑2 spike proteins). This gives your immune system the opportunity to learn how to fight off SARS‑CoV‑2 without ever needing to be exposed to it. Its ingredients and their purposes are explained below (Pfizer, 2021).

30 mcg nucleoside-modified mRNA encoding the SARS‑CoV‑2 spike protein : This is the genetic material that serves as the main ingredient of the vaccine. The term "nucleoside-modified" signifies that a compound commonly found in RNA called uracil has been substituted with a compound called pseudouridine. The use of pseudouridine in mRNA-based therapeutics and preventatives was suggested by Drs. Katalin Karikó and Drew Weissman in 2005 to solve earlier complications resulting in excessive immune responses (Garde & Saltzman, 2020). If you've heard that mRNA vaccines have never been used in humans before because the animals in animal trials died, that is in reference to studies performed before pseudouridine started being substituted for uracil. Human trials using mRNA-based therapeutics and preventatives have been ongoing since 2008 (Weide, Carralot, et al., 2008; Weide, Pascolo, et al., 2009; Xu et al., 2020).

0.77 mg lipids : The following fats form the lipid nanoparticles responsible for protecting the mRNA while the vaccine is frozen for storage and transport then thawed before injection. This blend of fats also matches the outside of our muscle cells, helping guide the mRNA to the correct place once the vaccine has been injected. Lipid nanoparticles are classically composed of four types of fats: one to hold the mRNA in place, two to give it its structure, and one to keep it stable (Cross, 2021; McCoy, 2021).

• [(4-hydroxybutyl)azanediyl]di(hexane-6,1-diyl) bis(2-hexyldecanoate) : Also known as ALC‑0315, this lipid holds the mRNA in place until the particle meets an appropriate cell for the mRNA to be delivered into.

• 2[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide : Also known as ALC‑0159, this lipid keeps the particle stable and protects the mRNA.

• 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) : Also known as distearoylphosphatidylcholine, this lipid helps form the structure of the particle.

• cholesterol : Cholesterol is a naturally occurring fat that is present in every cell of the body, making it an ideal choice when fats are required. In this application, cholesterol is used to help maintain the structure of the particle.

0.01 mg potassium chloride : This is a salt. It is used as a stabilizer to protect the vaccine when it is frozen and to help balance the acidity of the solution (U.S. Food and Drug Administration [FDA], 2019; Ravell, 2021).

0.01 mg monobasic potassium phosphate : This is a salt. It is used as a stabilizer to protect the vaccine when it is frozen and to help balance the acidity of the solution (FDA, 2019; Ravell, 2021).

2.52 mg sodium chloride : This is a salt. It is used as a stabilizer to protect the vaccine when it is frozen and to help balance the acidity of the solution (FDA, 2019; Ravell, 2021). 0.36 mg comes from the vaccine itself, while an additional 2.16 mg comes from the sterile saline used to dilute the vaccine prior to injection.

0.07 mg dibasic sodium phosphate dihydrate : This is a salt. It is used as a stabilizer to protect the vaccine when it is frozen and to help balance the acidity of the solution (FDA, 2019; Ravell, 2021).

6 mg sucrose : This is a sugar that is routinely used as a stabilizer in vaccines that undergo freezing (FDA, 2019; Ravell, 2021).

The Pfizer-BioNTech COVID‑19 Vaccine EUA Fact Sheet for Recipients and Caregivers can be downloaded as a PDF from Pfizer here.

Moderna COVID‑19 Vaccine

Authorized for use on December 18, 2020, the Moderna COVID‑19 vaccine consists of strands of messenger RNA (genetic instructions) coated in lipid nanoparticles (tiny blobs of fat) that temporarily teach some of your cells how to make a substance that is nearly identical to bumps found on the surface of the virus that causes COVID‑19 (SARS‑CoV‑2 spike proteins). This gives your immune system the opportunity to learn how to fight off SARS‑CoV‑2 without ever needing to be exposed to it. Its ingredients and their purposes are explained below (Moderna, 2021).

100 mcg nucleoside-modified mRNA encoding the SARS‑CoV‑2 spike protein : This is the genetic material that serves as the main ingredient of the vaccine. The term "nucleoside-modified" signifies that a compound commonly found in RNA called uracil has been substituted with a compound called pseudouridine. The use of pseudouridine in mRNA-based therapeutics and preventatives was suggested by Drs. Katalin Karikó and Drew Weissman in 2005 to solve earlier complications resulting in excessive immune responses (Garde & Saltzman, 2020). If you've heard that mRNA vaccines have never been used in humans before because the animals in animal trials died, that is in reference to studies performed before pseudouridine started being substituted for uracil. Human trials using mRNA-based therapeutics and preventatives have been ongoing since 2008 (Weide, Carralot, et al., 2008; Weide, Pascolo, et al., 2009; Xu et al., 2020).

1.93 mg lipids : The following fats form the lipid nanoparticles responsible for protecting the mRNA while the vaccine is frozen for storage and transport then thawed before injection. This blend of fats also matches the outside of our muscle cells, helping guide the mRNA to the correct place once the vaccine has been injected. Lipid nanoparticles are classically composed of four types of fats: one to hold the mRNA in place, two to give it its structure, and one to keep it stable (Cross, 2021; McCoy, 2021).

• SM-102 : This lipid holds the mRNA in place until the particle meets an appropriate cell for the mRNA to be delivered into.

• polyethylene glycol (PEG) 2000-dimyristoyl glycerol (DMG) : Also known as PEG2000‑DMG, this lipid keeps the particle stable and protects the mRNA.

• cholesterol : Cholesterol is a naturally occurring fat that is present in every cell of the body, making it an ideal choice when fats are required. In this application, cholesterol is used to help maintain the structure of the particle.

• 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) : Also known as distearoylphosphatidylcholine, this lipid helps form the structure of the particle.

0.31 mg tromethamine : This is an acid stabilizer used to help balance the acidity of the solution (Ravell, 2021).

1.18 mg tromethamine hydrochloride : This is an acid stabilizer used to help balance the acidity of the solution (Ravell, 2021).

0.043 mg acetic acid : This is an acid used to help balance the acidity of the solution (Ravell, 2021).

0.20 mg sodium acetate trihydrate : This is a salt. It is used as a stabilizer to protect the vaccine when it is frozen and to help balance the acidity of the solution (FDA, 2019; Ravell, 2021).

43.5 mg sucrose : This is a sugar that is routinely used as a stabilizer in vaccines that undergo freezing (FDA, 2019; Ravell, 2021).

The Moderna COVID‑19 Vaccine EUA Fact Sheet for Recipients and Caregivers can be downloaded as a PDF from Moderna here.

Johnson & Johnson/Janssen COVID‑19 Vaccine

Authorized for use on February 27, 2021, the Johnson & Johnson/Janssen COVID‑19 vaccine contains a specially engineered virus that delivers genetic instructions to temporarily teach some of your cells how to make a substance that is nearly identical to bumps found on the surface of the virus that causes COVID‑19 (SARS‑CoV‑2 spike proteins). This gives your immune system the opportunity to learn how to fight off SARS‑CoV‑2 without ever needing to be exposed to it. Its ingredients and their purposes are explained below (Janssen Therapeutics, 2021).

50 billion adenoviral particles expressing the SARS‑CoV‑2 spike protein : This is the specially engineered virus that serves as the main ingredient of the vaccine. This virus is replication incompetent (information on replication competence can be found in my earlier post, "COVID‑19 Vaccines Cannot 'Shed'"), so it can't infect you or cause you to "shed" virus.

0.14 mg citric acid monohydrate : This is an acid used to help balance the acidity of the solution (Jones, 2021).

2.02 mg trisodium citrate dihydrate : This is a base used to help balance the acidity of the solution (Jones, 2021).

2.04 mg ethanol : This is an alcohol that, when used at a low strength, prevents the virus from breaking down (Jones, 2021).

25.5 mg 2-hydroxypropyl-β-cyclodextrin (HBCD) : This is a sugar that is used to stabilize the solution and keep it in a liquid state (FDA, 2019; Jones, 2021).

0.16 mg polysorbate-80 : This is a common emulsifier used to prevent the ingredients from separating (Jones, 2021).

2.19 mg sodium chloride : Sterile saline is a byproduct of a chemical reaction that happens during the manufacture of this vaccine. The saline contributes water and sodium chloride to the vaccine (Jones, 2021).

The Johnson & Johnson/Janssen COVID‑19 Vaccine EUA Fact Sheet for Recipients and Caregivers can be downloaded as a PDF from Janssen here.

Conclusion

These vaccines are new, but they don't need to be scary; each one of them is built upon decades of solid research. mRNA vaccines have been used in the treatment of certain cancers for over a decade (Weide, Pascolo, et al., 2009), and Johnson & Johnson/Janssen's adenoviral vector vaccine technology is used in an Ebola vaccine that has received full approval in the European Union (European Commission, 2020). Lipid nanoparticles are already used in an FDA-approved medication called Onpattro (patisiran), which treats an otherwise fatal genetic disease; Onpattro has been FDA-approved since 2018 (Alnylam Pharmaceuticals, 2021). These vaccines are preservative-free, they do not contain mercury or aluminum, and the vials they come in are latex-free (Janssen Therapeutics, 2021; Moderna, 2021; Pfizer, 2021).

Virtually all injectable medications that I have encountered include salts, acids, bases, and stabilizers; they keep the pH of the liquid close to that of the human body, ensuring that the medication doesn't cause tissue damage or burn when it's injected. Many of these ingredients are even things that you probably consume on a regular basis: sodium chloride is just table salt, potassium chloride is a salt replacement commonly used by people on sodium-restricted diets, sucrose is just table sugar, and acetic acid is just vinegar. The only difference is that these ingredients are pharmaceutical-grade, ensuring that they are sterile and pure.

Hopefully this post has helped explain what the ingredients in each vaccine are and why they are there. The vaccine makers and regulatory agencies aren't intentionally trying to hide things or confuse you; they're just full of scientists who like big words. Be safe out there!