Vaccine Safety – COVID-19 Vaccine

In this series, we're exploring vaccines, the ingredients found in vaccines, and vaccine safety. In this post, we look at the currently available COVID-19 vaccines in the U.S. and the ingredients that make up these vaccines.

What are vaccines?

A vaccine is a biological preparation designed to provide our body with active immunity to particular infectious pathogens when appropriately administered.

Vaccines stimulate immunological memory. Once we've received a vaccine, our body's immune system can recall a specific pathogen's identity, even years later, and effectively fight the pathogen.
You can learn more about how vaccines work, ingredients in vaccines, and general comments about their safety in our previous blog posts (1,2).

What type of vaccine is the COVID-19 vaccine?

Due to the urgency to develop a vaccine against COVID-19, various approaches have been employed, both established and novel, by numerous pharmaceutical companies. To date, two vaccines have been approved by the US Food and Drug Administration. Both of these approved COVID-19 vaccines have capitalized on a novel strategy to develop what is termed a messenger ribonucleic acid (mRNA) vaccine.
An mRNA vaccine provides instructions to our cells to produce harmless proteins that trigger an immune response.

How do the COVID-19 mRNA vaccines work?

Like most viruses, the virion of the SARS-CoV-2 virus that causes COVID-19 contains a ribonucleic acid (RNA) center coated in an envelope of protein and fat.
Once a virus enters a host (our body), the protein binds to the host's healthy cells, facilitating the entry of viral RNA into host cells and forces the healthy cells to produce copies of the virus. When this occurs, we have an infection.
As we've discussed in a prior blog post, once we're infected, our body's white blood cells multiply to stop the virus, but that takes time (1). While most healthy individuals successfully fight off COVID-19 infections, many individuals with underlying health concerns cannot fight off the infection, causing them to succumb to the disease.
We know our body’s immune system can destroy the virus if given enough time. The COVID-19 mRNA vaccine primes our body to respond more effectively by expanding those cells that can recognize and then destroy the SARS-CoV-2 virus.
Unlike attenuated vaccines that use weakened pathogens to prime our immune system to fight infection, the COVID-19 mRNA vaccines do NOT contain any SARS-CoV-2 virus.
Instead, they contain mRNA that gives our cells instructions to make a harmless-to-us piece of protein that’s the same as the protein present in the SARS-CoV-2 virus. The protein then teaches our immune cells to identify and combat the SARS-CoV-2 virus.
Once our body makes the harmless-to-us protein, our body breaks down the instructions (mRNA) and eliminates the instructions from our body, leaving our body with the protein.
Next, our body’s immune system will recognize the protein as foreign (i.e., doesn’t belong to us) and develop an immune response including antibodies to destroy the protein. As we’ve covered in a prior post, our body’s immune system remembers how to fight and eliminate unwanted pathogens.
Now that our body’s immune system knows how to destroy the protein found on the SARS-CoV-2 virus that causes COVID-19 infections, if we are exposed to COVID-19, our body has been trained to identify and destroy the protein that keeps the SARS-CoV-2 virus viable and thus protect us from the virus (1).

What ingredients are in the COVID-19 vaccine?

There are two vaccines available today: one from Pfizer-BioNTech and one from Moderna. Both vaccines are mRNA vaccines.

Pfizer-BioNTech Vaccine Ingredients (1)
Active ingredient:

  • Messenger ribonucleic acid (mRNA)

Lipids (fats):

  • (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 

Stabilizers (buffer solution and salts):

  • potassium chloride
  • monobasic potassium phosphate
  • sodium chloride
  • dibasic sodium phosphate dihydrate 


  • sucrose

Moderna Vaccine Ingredients (1)
Active ingredient:

  • Messenger ribonucleic acid (mRNA)

 Lipids (fats):

  • SM-102
  • polyethylene glycol [PEG] 2000 dimyristoyl glycerol [DMG]
  • cholesterol
  • 1,2-distearoyl-sn-glycero-3-phosphocholine [DSPC]

Stabilizers (buffer solution and salts):

  • tromethamine
  • tromethamine hydrochloride
  • acetic acid
  • sodium acetate 


  • sucrose

What ingredients are NOT in the COVID-19 vaccine?

We’ve noticed some misleading information about the ingredients present in vaccines making the rounds on social media channels and blogs. We believe it’s important to dispel some of these unfounded claims (1,2,3,4).

  • COVID-19 virus is NOT in the vaccine.
  • Fetal cells are NOT in the vaccine.
  • Human blood and tissue products are NOT in the vaccine.
  • Egg products are NOT in the vaccine.
  • Preservatives (e.g., mercury, thimerosal) are NOT in the vaccine.
  • Antibiotics are NOT in the vaccine.
  • Latex products are NOT in the vaccine and were not used in production.
  • Pork products are NOT in the vaccine.
  • Microchips are NOT in the vaccine.

How effective is the vaccine?

When administered properly, the Pfizer-BioNTech Vaccine is 95% effective in preventing COVID-19 infections in all individuals ages 16 and above (1).
When administered properly, the Moderna Vaccine is 95% effective in preventing COVID-19 infections in all individuals ages 18 and above (1).

Have the vaccines been tested, and are they safe?

While these may be new vaccines, released in an emergent circumstance, the U.S. Food and Drug Administration (FDA) still has strict quality, safety, and efficacy requirements that Pfizer-BioNTech and Moderna met (1). 
Tens of thousands of individuals received the vaccines by participating in clinical studies to ensure the vaccines' safety and efficacy (1).
Based on the current data, both vaccines are safe and effective in preventing severe COVID-19 infections.

Has anyone died from getting the vaccine?

At the time of publication, there are no confirmed cases of an individual dying due to the COVID-19 vaccines.
There have been a handful of adverse reactions that have required immediate medical assistance, so it's important to talk with your doctor before getting vaccinated if you have a history of adverse reactions to vaccines.
Sadly, more than 410,000 Americans have died from complications related to COVID-19 infections.

Who benefits most from the COVID-19 vaccines?

Though society as a whole benefits from herd immunity, which results from widespread vaccination, there are subgroups that are more acutely impacted by COVID-19 infections:

  • adults 65 and older (1)
  • individuals with medical conditions such as cardiovascular disease, diabetes, chronic respiratory conditions, obesity, compromised immune systems, and more (1).

Can anyone receive a vaccine?

At the time of publication, the COVID-19 vaccine supply is still somewhat limited as production continues to gear up, so government health agencies are prioritizing vaccine distribution based on an individual's risk factors, occupation, age, and other specific criteria.
Individuals who've had an allergic reaction to vaccines in the past or who have specific health conditions should speak with their doctor before receiving a vaccine.

How can I sign-up to get vaccinated?

At the time of publication, vaccine distribution is routing through local health departments but may vary, state to state.
To learn more about the COVID-19 vaccine distribution process in your area, reach out to your local health department.

The good news.

We have safe, effective vaccines able to help protect us from COVID-19. With wide-spread vaccination and other best health practices like hand washing, mask-wearing, and social distancing, we can stop the spread of COVID-19.



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