Center for Research on Ingredient Safety

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 vaccines in our previous blog post.

What do I need to know about vaccine ingredients?

It’s important to keep in mind that vaccines are developed not to harm people, rather to protect people from dangerous and sometimes deadly diseases.

There are some ingredients you’ll see on this list that are commonly found in our diets, cosmetics, and other products we use daily. Other ingredients will be unfamiliar and may sound scary or intimidating, this doesn’t mean they are harmful.

The potency is important when looking at vaccines, but it’s also important to keep in mind that the dose makes the poison and the vast majority of these vaccines will contain incredibly small amounts of an ingredient at a potency level designed to help, rather than harm us.

The goal is not to cause harm. The goal is to protect people.

What types of ingredients do we find in vaccines?

There are numerous types of vaccines. These vaccines typically contain ingredients in four core areas.

• Antigens: Active ingredients designed to elicit an immune response and immunological memory to protect against specific pathogens

• Adjuvants: ingredients that enhance the immune response

• Stabilizers: additives that protect the integrity of the active ingredient(s) during manufacturing, storage, and transportation

• Preservatives & Antibiotics: These ingredients are used in some vaccines to prevent bacterial and fungal growth  

What are antigen ingredients?

It helps to think of antigen ingredients as the active ingredient giving our immune system instructions. The other ingredients are designed to enhance and protect the antigen.

Antigen ingredients are often a weakened form of the pathogen (attenuated vaccine), a dead version of the pathogen (inactivated vaccine), a specific piece of the pathogen (subunit, recombinant, polysaccharide, or conjugate vaccine), or inactivated toxin (toxoid vaccines). 

Sometimes the active ingredient in a vaccine is the genetic material (DNA or mRNA) that gives instructions to our body to produce specific, harmless proteins that will train our immune system to recognize and combat the pathogen. 

Overall, the antigen ingredients of a vaccine do not contain fully active pathogens or toxins; therefore, we will not contract the disease directly from the vaccine.

There are more than 60 vaccines containing different antigen ingredients. Since there are so many we cannot cover each specific antigen ingredient in this post. However, the U.S. Food and Drug Administration has a database that allows you to look up vaccines. And, the U.S. Centers for Disease Control and Prevention (CDC) provides more in-depth information about vaccine ingredients in their Pink Book.

Antigen ingredients cannot complete the job without additional ingredients that help enhance and protect the antigen called excipient ingredients.

Excipient ingredients are just as important as antigen ingredients. These ingredients are the adjuvants, stabilizers, preservatives, and antibiotics (1). 
 

Let’s take a look at adjuvant ingredients.

Adjuvant ingredients are necessary in some vaccines to help enhance our immune response when we receive a vaccine. The enhanced response helps our bodies build immunity by expanding the white blood cells that recognize the specific pathogen against which we have been vaccinated.
 
Below are commonly found adjuvant ingredients approved for use by the FDA.

• Aluminum salts: Aluminum is one of the most common metals found in nature and is found naturally in our air, food, and water. Aluminum salts in vaccines are a group of aluminum-containing ingredients that have been safely used in vaccines for more than 70 years to help boost the efficacy of a vaccine (1,2,3)

• CpG 1018: This ingredient is a synthetic form of DNA that mimics bacterial and viral genetic material to boost vaccine effectiveness (1,2)

• MF59: This ingredient is an oil and water emulsion of squalene. Squalene is found naturally in many plants and animal cells, including humans (1,2,3)  

• QS-21: This ingredient is a naturally occurring compound extracted from the Chilean soapbox tree (1)

• AS01B: This ingredient is made up of monophosphoryl lipid A (MPL), an immune-boosting substance isolated from the surface of bacteria, and QS-21 (1,2)

Let’s take a look at stabilizing ingredients.

Stabilizing ingredients are needed to keep vaccines safe and effective by helping to protect from heat, light, humidity, acidity, and more. Without these ingredients, vaccines may easily breakdown and lose their effectiveness (1).
 
There are numerous types of stabilizing ingredients broken down into three categories:

• Sugars (e.g., sucrose, lactose)

• Amino Acids (e.g., glycine or the monosodium salt of glutamic acid)

• Proteins (e.g., human serum albumin or gelatin) 

Many of these ingredients are often found in our diets, cosmetics, and other commonly used products.
 

Let’s take a look at preservative and antibiotic ingredients.

Preservative and antibiotic ingredients are needed to prevent bacterial or fungal growth that could impact vaccine efficacy or adversely impact human health. 

Today, many vaccines are packaged in a way that doesn’t require preservatives so there are fewer preservative ingredients added to vaccines (1). 

Some vaccines do still use preservative ingredients to stay safe. The most common ingredient is thimerosal, occasionally phenol, 2-phenoxyethanol, and benzethonium chloride are used as preservative agents in vaccines (1).  

• Thimerosal preservative found in vaccines is a compound that contains mercury, a naturally occurring metal. There are two types of mercury and our bodies process each differently: methylmercury and ethylmercury (1). 

  Methylmercury can cause harm to people at high levels. Ethylmercury, the kind found in Thimerosal, is cleared quickly in the body and unlikely to cause harm when used in vaccines (1,2,3).  

• Phenol preservative is used in three FDA-approved vaccines, however, these vaccines are not part of routine vaccination (1).

• 2-Phenoxyethanol preservative found in one vaccine to protect against polio (1). 

• Benzethonium chloride preservative is also used in one vaccine, again, this vaccine is not part of routine vaccination (1).

Antibiotics are used in some vaccines during the manufacturing process to help prevent unwanted bacterial growth and contamination.

The antibiotics used in vaccine products are typically neomycin, polymyxin B, streptomycin, or gentamicin. These antibiotics are used because they are less likely to cause allergic reactions (1). 
 

Can everyone get vaccinated?

No, not everyone can receive vaccines for various health reasons including allergic reactions or other health concerns.
 
It’s important that people who can receive vaccines do receive vaccination so we can build the herd immunity needed to prevent community spread of vaccine-preventable communicable diseases.
 

How do we know vaccines are safe?

Before wide distribution, an FDA-approved vaccine goes through a 7-step development and approval process that includes safety testing and evaluations in laboratories and clinical trials in human volunteers to ensure its safety and efficacy (1).
 

The good news.

While some of these ingredients are unfamiliar, ingredients in vaccines have been studied extensively by the FDA and other research and regulatory agencies for safety and efficacy.
 
We can trust that the benefit of getting vaccinated outweighs the potential harm of the diseases we could contract