Vaccines have saved over 150 million lives in the last 50 years, making them one of the most important advancements in modern medicine. But concerns about vaccine ingredients have been around for decades.
Here’s everything you need to know about vaccine ingredients and how we know they are safe.
Every ingredient is rigorously tested for safety
Vaccines go through multiple rounds of safety testing before being approved for public use. This testing includes clinical trials involving thousands of participants to assess vaccine safety and effectiveness.
The Food and Drug Administration oversees clinical trials and reviews data to ensure all new vaccines are safe before approval. The Centers for Disease Control and Prevention also evaluates safety before recommending vaccines to the public. After a vaccine is approved, both agencies monitor and investigate any potential safety concerns that may arise.
Vaccine manufacturers test every batch to ensure they work properly and are free of contamination. Additionally, the FDA tests and approves all ingredients before they are used in vaccines. Ingredient lists for FDA-approved vaccines are publicly available online.
Types of vaccine ingredients and what they do
Every vaccine ingredient is there for a reason. Some ingredients make vaccines more effective or safer. Others enhance the vaccines’ ability to trigger an immune response, allowing for lower doses.
Antigen
The only active ingredient in a vaccine is the antigen, which trains the immune system to recognize and fight the virus or bacteria the vaccine protects against. A vaccine antigen may be a weakened, inactivated, or fragmented virus or bacteria. In the case of DNA or RNA vaccines, the antigen provides instructions for cells to produce a fragment of the target virus or bacteria. Vaccines also contain stabilizers like sugar to prevent the antigen from breaking down.
Adjuvant
An adjuvant is an ingredient that boosts the body’s response to a vaccine, making the vaccine more effective and reducing the dose needed for protection.
“Researchers realized that adjuvants allowed you to use smaller vaccine doses,” wrote Dr. Christopher Labos, a cardiologist and epidemiologist at McGill University, in a 2019 article. “As a result, although we have more vaccines in total, the amount of antigens (bacteria and viruses) used in vaccines has been decreasing over time.”
Preservatives
Because many vaccines are administered in vials with multiple doses, extra care must be taken to prevent dangerous contamination. Preservatives are added to vaccines to prevent the growth of bacteria and fungi.
These ingredients were added to vaccines in the early 1900s after several instances of children being seriously injured or killed by bacterial infections linked to contaminated vaccines. Now, all vaccines are tested for contamination.
Production byproducts
Many ingredients go into the making of vaccines. Some are used to grow antigens and bind ingredients together, while others prevent contamination during production. Traces of these ingredients may remain in the vaccine in tiny amounts that are not harmful to humans.
Aluminum
Aluminum is an adjuvant added to vaccines to safely boost effectiveness. The element, which occurs naturally in the environment, is one of the most common on Earth. The amount of aluminum the FDA allows in vaccines is considerably less than what is found in breast milk and baby formula.
“We’re exposed to aluminum constantly,” said Dr. Tony Moody, director of the Duke CIVICs Vaccine Center, to the New York Times. “If you inhale dust from the outside, you’re coming into contact with aluminum.”
Many foods we eat daily contain high levels of aluminum, including cocoa, milk, cheese, grains, tea, and certain fruits and vegetables. Infants and children get far more aluminum through their diet than through vaccinations.
A 2011 study concluded that exposure to the tiny amount of aluminum in vaccines is “extremely low risk to infants” and that the benefits of vaccination far outweigh any “theoretical concerns.”
Mercury
Thimerosal is a vaccine preservative that prevents contamination. Because it contains a form of mercury that is harmless to humans in low doses, it has been a frequent target of anti-vaccine claims.
In 1999, the FDA concluded that thimerosal in vaccines was not harmful but removed the ingredient from all childhood vaccines to be safe. Since 2001, only certain flu vaccines contain thimerosal at a dose roughly equivalent to the amount of mercury in a can of tuna.
DNA fragments
Small pieces of DNA are sometimes used to make active ingredients in vaccines. Trace amounts of this DNA may remain in the vaccine after production. However, their small quantity and size prevent them from interacting with DNA in the body.
Formaldehyde
Formaldehyde kills bacteria and viruses that can contaminate vaccines. Most of the preservative is removed during manufacturing, but negligible amounts may remain in doses that are completely safe for humans.
Formaldehyde occurs naturally in many living things, including humans. In fact, infants naturally have more formaldehyde in their bodies at any given moment than they will be exposed to from all of their vaccinations combined. A single pear contains 60 times more formaldehyde than any childhood vaccine.
Fetal cells
No vaccine on the market contains fetal cells. However, fetal tissue collected in the 1960 and 1970s was used to develop some vaccines. Researchers have also used these cells for decades to develop medications, including most over-the-counter pain, cold, and allergy medicines.
“Those cells that were obtained from those elective abortions have been used to make several vaccines,” said pediatrician and vaccine expert Dr. Paul Offit in a video series produced by the Children’s Hospital of Philadelphia. “It’s the same cells that were obtained in the early 1960s, so no new therapeutic or elective abortions have been performed since then for the purpose of making vaccines.”
For more information about vaccine ingredients, talk to your health care provider.