Health: Vaccines contain five main types of ingredients, each with a purpose

Tracey Flower
Special to the Daily
Daniel LeBlanc, of Gypsum, receives a tetanus vaccination from Tania Engle, a physician's assistant at the Edwards Walk-In Clinic inside Shaw Regional Cancer Center.
Lexi Christensen | Special to the Daily |

Editor’s note: This is the second part of a two-part series of articles about vaccines. Find the first part, focusing on vaccine side effects, at Send questions and comments about this article to Krista Driscoll at

Physicians and public health officials alike often hail vaccines as one of the greatest public health achievements of the 20th century. Public scrutiny of vaccines has grown in recent years, though, as concerns about what’s in vaccines, and whether those ingredients have the potential to cause more harm than good, have risen.

Vaccines undergo some of the most rigorous testing of any medication to ensure their safety and that the benefits far outweigh any risks. This means that for any available vaccine, the U.S. Food and Drug Administration has determined that the substances used in its manufacturing and contained in the end product are also safe in the quantities found in the vaccine. Information about these ingredients is readily available from the Centers for Disease Control and Prevention.

“First of all, what’s important to understand is that the ingredients list for vaccines is very transparent,” said Rebecca Larson, manager for the Disease Prevention and Control Department at Eagle County Public Health and Environment. “You can pull it up and find out exactly what’s in every vaccine and the amount. So there isn’t a hidden secret.”

“The most prevalent myth is that the flu shot causes the flu or other respiratory illness. Since there is no live virus in the flu vaccine, this is not possible.”Dr. Dennis Lipton Internal medicine at Vail Valley Medical Center

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Vaccines are composed of ingredients from five categories: antigens, adjuvants, stabilizers, preservatives and manufacturing by-products. Not every vaccine contains ingredients from all five categories, but understanding their purpose in any given vaccine can be a helpful first step to gaining a better understanding about vaccine ingredients.

“Vaccines are made of kind of a variety of things,” Larson said. “We have the antigens, which kill viruses or bacteria, and then adjuvants, which help stimulate a stronger immune response to the vaccine. … Vaccines also have stabilizers, which keep the vaccine potent while they’re in transportation and storage — those are usually either sugars or gelatins — and then some vaccines, not many, have preservatives to prevent contamination from bacteria.”

The Children’s Hospital of Philadelphia’s Vaccine Education Center breaks it down in detail on its website, explaining that antigens are considered the active part of the vaccine because they are the parts of the vaccine to which an immune response is generated. Most often, these components are whole viruses or bacteria, parts of the viruses or bacteria or products made by bacteria, called toxins.

Vaccines today contain fewer antigens than those from a few decades ago, Larson said.

“Sometimes what people don’t realize is the vaccines we use today have fewer antigens — so that’s the viruses and bacteria that protect us from the disease — than the vaccines of generations ago,” she said. “So that means they’re even better and safer now than they were generations ago.”

Flu shots don’t cause the flu

There has been a rise in concern in recent years that those vaccines containing live viruses can cause the disease they were designed to prevent. This, said, Colorado State Epidemiologist Dr. Rachel Herlihy, is a myth.

“There are a few vaccines, like MMR (measles, mumps, and rubella), varicella and rotavirus vaccine that are live or extenuated or weakened virus vaccines,” said Herlihy, who is also a physician trained in preventive medicine and oversees the Colorado Department of Public Health and Environment’s communicable disease and immunization branches. “But in the case where there’s not even live virus, there’s not even a disease to be transmitted. Nothing can occur. And that’s really the majority of childhood vaccines.

“The small number of vaccines that contain live viruses, those viruses are really weakened to an extent that they really cannot cause disease in the person that’s receiving them. There are very rare cases where that can occur, and that’s much more likely to happen if someone has, for example, a weakened immune system.”

A common concern, and associated myth, Herlihy said, is that the flu vaccine causes the flu. This, she said, is impossible because the flu vaccine does not contain a live virus. Dr. Dennis Lipton, who practices internal medicine at Vail Valley Medical Center, explained why this may have become a concern and, subsequently, a myth.

“The most prevalent myth is that the flu shot causes the flu or other respiratory illness,” Lipton said. “Since there is no live virus in the flu vaccine, this is not possible. The flu shot is given at the beginning of cold and flu season. Statistically, in any given week, a certain percentage of people will get a respiratory virus during that time of year. Since a large number of people get the flu shot around that time, they tend to blame the vaccine. Statistics indicate no greater risk of getting sick if you get the shot.”

‘Aluminum is everywhere’

The reason vaccines can be effective with fewer antigens is because of adjuvants like aluminum salts. According to the Children’s Hospital of Philadelphia’s Vaccine Education Center, adjuvants are substances that allow vaccines to work better by enhancing the immune response to the vaccine. Their presence also means you need fewer doses of a vaccine for it to be effective.

“Aluminum in vaccines … helps stimulate your immune system,” Herlihy said. “So it means you need less of the antigen, less of the virus, less of the bacteria in the vaccine, if you add some aluminum to stimulate the immune system.”

According to Immunize for Good, a website run by the Colorado Children’s Immunization Coalition, a growing awareness amongst parents about the presence of aluminum in some vaccines has had some people wondering whether the recommended childhood vaccination schedule results in too much exposure to aluminum and whether an alternate schedule, like that laid out by Dr. Robert Sears in “The Vaccine Book,” might be safer.

However, as stated by Immunize for Good, and confirmed by Herlihy, aluminum is one the most common elements found in nature and is part of our everyday environment. The amount of aluminum delivered through a vaccination, said Herlihy, is less than what is delivered to an infant through his or her food.

“Aluminum is everywhere,” said Herlihy. “It’s in plants, it’s in soil, it’s in water, it’s in the air we breathe — it’s absolutely everywhere. And if you look at all of the shots combined that an infant might receive in the first 6 months of life, they receive about 4 milligrams of aluminum in all of those combined.

“So if you look at how much aluminum is in breast milk during that same six-month period of time, it’s really 7 (milligrams) to 10 milligrams and then if you have a formula-fed infant, it’s up to 38 milligrams. So the amount of aluminum that an infant is receiving through vaccines is really quite small compared to what they’re receiving just from their daily life.”

According to the Children’s Hospital of Philadelphia’s Vaccine Education Center, you are likely to have more aluminum in your system if it’s injected, versus being ingested through food, for example. But even though there is that difference between injection and ingestion, the amount that is ingested is logarithmically so much more than what is delivered in a vaccination, that you have more aluminum in your circulation because of what you eat and drink than from vaccines.

Understanding thimerosal

Stabilizers are used in vaccines to protect the integrity of the active ingredients during manufacturing, storage and transport. Preservatives are used in some vaccines to prevent bacterial or fungal contamination.

Thimerosal, a mercury-containing preservative, has come under scrutiny in the United States in recent decades and, as a result, in 2001 it was removed from all vaccines routinely recommended by the CDC for children younger than 6. The only exception is the flu vaccine, and parents have the option of requesting a thimerosal-free version of this vaccine if they have concerns about thimerosal.

According to Immunize for Good, the primary cause for concern about thimerosal for many parents is that mercury is known to be harmful to humans. However, there are different types of mercury, ethyl mercury and methyl mercury. Thimerosal is an ethyl mercury, whereas the mercury found in something like tuna fish is methyl mercury.

This distinction is an important one to make, Herlihy said.

“So methyl mercury is the type of mercury that we worry about that’s in fish and our environment; ethyl mercury is thimerosal,” Herlihy said. “If you look at, for instance, ethanol, which is the alcohol that I enjoy in a glass of red wine, that is something that I can ingest and it’s not poison to me … but then there’s something called methanol, which is wood alcohol and causes blindness. Just because that root word is in there does not mean that the substances are the same thing and have the same health effects; that’s important to keep in mind.”

Manufacturing byproducts

The fifth category of vaccine ingredients, manufacturing byproducts, refers to substances — chemicals and cell byproducts — that are used during the manufacturing process for some vaccines and then removed; though they’re removed, minute amounts may remain in the end product. An example of one of these byproducts is formaldehyde.

According to Immunize for Good, formaldehyde inactivates bacterial products for toxoid vaccines, which are vaccines that use an inactive bacterial toxin to produce immunity. It also kills unwanted viruses and bacteria that might contaminate the vaccine during production.

While formaldehyde can be dangerous to humans at high quantities, the substance actually occurs naturally in our bodies.

“Formaldehyde, again, is a substance that our bodies are very familiar with,” Herlihy said. “We produce our own formaldehyde; formaldehyde is a natural byproduct of cellular activity. So our cells produce formaldehyde just by us living.

“Our blood stream has about 50 to 70 times the amount of formaldehyde that a baby would get from a single vaccine. If you inject a baby with formaldehyde in a vaccine, that infant’s body doesn’t even register the difference in that amount of formaldehyde.”

Ultimately, say physicians and public health experts, the best resource for individuals who have questions or concerns about the ingredients found in vaccines recommended for them or their children is their family’s doctor.

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