Vaccine Ingredients

This is an important topic with parents today, as it should be. Unfortunately, the topic of vaccine ingredients  can be very confusing because there is so much misinformation, and information taken out of context. Let’s face it, few of us parents have time to pursue a chemistry degree between diaper changes.

Every day we are exposed to a myriad of chemicals and “toxins” in our environment. (Isn’t it great to live in a community that is cognizant of that and does its best to reduce exposure to harmful ones?) And obviously we want to be very careful about what we put not only in our bodies, but also what we put into the bodies of our loved babies and children.

When talking about additives and vaccine ingredients, people might use the word “toxin” without identifying what that means. Toxins are most commonly defined by dose or level of exposure. Water could be toxic if consumed in large quantities. Chlorine is a highly toxic chemical, but small amounts are needed to keep our tap water safe. Remembering the old saying “the dose makes the poison” helps to clarify the concept for many people.

Always know that there is no attempt to hide what goes into vaccines. The process is transparent, and you can find all the ingredients (PDF) used in childhood and adult vaccines from the Centers for Disease Control and Prevention (CDC).  Please note that the list also includes substances used in the manufacturing of vaccines, such as production media, which are removed from the vaccine but may leave trace amounts.

Additives and excipients used in the production of vaccines may include:

  • Suspending fluid (e.g. sterile water, saline or fluids containing protein)
  • Preservatives and stabilizers to help the vaccine remain unchanged (e.g. albumin, phenols and glycine)
  • Adjuvants or enhancers to help the vaccine be more effective

List of Vaccine Ingredients

We have provided information on some of the vaccine ingredients that parents find most concerning. This is not an exhaustive list, but it does cover some of the ones that have been consistently misunderstood by web and book authors.

Chick Embryos
Human Serum Albumin or Aborted Human Fetus Cells


Aluminum is everywhere. It is the third most common element on earth and can be found in the foods we eat, the air that we breathe and in our water. It is used in a number of common products, including many medicines. Small amounts of aluminum salt are added to certain vaccines as an adjuvant.  An adjuvant enhances the vaccine’s protective immune response.  

Not all vaccines contain aluminum, since an adjuvant may not be needed.

Vaccines that do not have aluminum include:

  • polio (IVP)
  • measles, mumps and rubella (MMR)
  • chickenpox (varicella)
  • meningococcal conjugate (MCV4 for teens and pre-teens)
  • influenza

The US-licensed vaccines for children that contain aluminum adjuvants are: DTP, DTaP, some HiB, Hepatitis B, Hepatitis A and HPV.

All infants are exposed to aluminum in the environment. Breast milk, for example, contains approximately 40 micrograms (mcg) of aluminum per liter, and infant formulas contain an average of approximately 225 mcg of aluminum per liter. Among other factors, the toxicity of aluminum is dependent upon the amount and duration of exposure, how it enters the body, and the individual’s health (kidney function, especially).

Many parents are concerned that aluminum being injected via a vaccination is much more dangerous than the aluminum being ingested by mouth. But small amounts of ingested aluminum are also absorbed by the bloodstream, such as the aluminum found in breast milk.

Confusion around aluminum as a vaccine adjunct grew when vaccine critics began stressing that the FDA established much lower exposure limits for aluminum-contaminated products that are used to treat premature infants and others with poor renal function. That created more confusion than concern  about aluminum adjuvants used in vaccines. But, premature infants’ immature kidneys don’t excrete aluminum well. Unfortunately, these tiny patients must receive prolonged intravenous treatments with nutritional solutions and medications that are prone to significant aluminum contamination. People with kidney failure have developed serious neurological effects from aluminum accumulation, but only after exposure to high levels of aluminum over a period of many years during dialysis.

On the other hand, vaccines with aluminum are given to healthy infants with functional kidneys that readily excrete aluminum; they are administered under the skin or into the muscle, resulting in a delayed and gradual release of aluminum into the bloodstream; and, aluminum exposure from vaccination is periodic rather than prolonged.

While it is true that the body excretes almost all ingested aluminum (typically absorbing less than 1%) and that virtually all injected aluminum in vaccines eventually makes its way into the bloodstream, the authors of a 2011 FDA study applied updated parameters to a 2002 study by Keith and Chou and concluded: “The body burden of aluminum from a combination of vaccines and diet throughout an infant’s first year of life is significantly less than the corresponding safe body burden of aluminum, based on the minimal risk levels established by the Agency for Toxic Substances and Disease Registry.”

Avoiding aluminum exposure would be almost impossible since aluminum is so common in our natural environment. You should be concerned about your child’s aluminum exposure if they 1) have poor kidney function, and or 2) are exposed to very large quantities of aluminum for months or years. Since high exposure to aluminum is the result of occupational exposure (usually workers who work in dusty environments and breathe in aluminum dusts or fumes), you most likely will not need to worry about high environmental exposure.

Serious adverse effects attributable to the aluminum adjuvants are rare, but local reactions such as redness, swelling or tenderness at the injection site are not uncommon. Jefferson, et al, in a 2004 review of the evidence of adverse events after the DTP (diphtheria, tetanus and pertussis) which contains aluminum, found no evidence that aluminum salts cause any serious or long-lasting adverse events.


The Vaccine Education Center’s aluminum fact sheet (PDF)
The Children’s Hospital of Philadelphia’s aluminum page provides information about blood levels of aluminum after an injection
Agency for Toxic Substances and Disease Registry aluminum page

Chick Embryos

There are no chick embryos in vaccines. Vaccines that are created on egg media (a hen’s egg or its components) include those for measles, mumps and rubella (MMR), rabies, yellow fever and influenza.

Unlike the vaccines used to protect against bacterial diseases, vaccines that protect against diseases caused by a virus need a living cell in which to grow. By growing infectious pathogens in an egg, the virus becomes less pathogenic to humans. Each virus grows best in a certain area of the egg, or in an embryonic culture, and then undergoes multiple purification steps. Some residual egg proteins may be present in the final vaccine product. Since hens’ eggs are a common food in the American diet, this should not be concerning. In individuals who are hypersensitive to eggs, egg-containing foods can cause mild to severe allergic reactions, if ingested. These individuals may also have adverse reactions to vaccines produced on egg media.


If you ate an apple, a carrot or a banana today, your own body produced formaldehyde. And that same chemical (one carbon atom, two hydrogen atoms and one oxygen atom) is what is used in the manufacturing of vaccines and then diluted out. However, even after dilution, trace elements remain, which is why you might see formaldehyde listed on the ingredient label of a vaccine. But because it is the same chemical as what our body produces naturally, our bodies do not treat it any differently.

But why use such a scary chemical, one that we know to be dangerous, in vaccine manufacturing? Formaldehyde is used as an antimicrobial to prevent growth of germs or contamination of the vaccine. Because of those very antimicrobial properties, it  cannot be used in any of the “live” vaccines such as the MMR, rotavirus, varicella (chickenpox) and some flu vaccines. Instead, it is used to inactivate bacterial products for the toxoid vaccines such as diphtheria and tetanus. (These are vaccines that use an inactive bacterial toxin to produce immunity.)

Humans can consume 0.2mg per kilogram of weight (or 200 mcg per kilogram) of formaldehyde every day without seeing any adverse effects (view source). When setting these levels, the EPA uses a safety buffer of about 10-100 times, meaning that the true safe level for  daily exposure is likely around 2-20mg/kg every day. That’s a lot of formaldehyde.

So what’s the most a child might get in a single office visit? At their 6-month visit (when they are, on average, 16.5lbs or 7.5kg) a child receiving Hepatitis B, DTaP (diphtheria, tetanus, acellular pertussis), IPV (polio) and the flu vaccine would be getting a total of 307.5 micrograms (mcg). This is still far less than what is naturally found in the human body. At any given time, an average newborn would have about 575-862mcg of formaldehyde circulating in their blood naturally. You can also compare this to a single apple, which contains 428.4-1,516.4mcg (.43-1.51mg) of formaldehyde.  Formaldehyde does not build up in the body; within hours it is metabolized and eliminated as formate in the urine or breathed out as CO2.

Human Serum Albumin or Aborted Human Fetus Cells

For an idea to gain traction, even a false idea, there must be a grain of truth to it. So, the truth here is that some vaccines use viruses that were grown in human cells. Why? A virus must be given a medium in which to propagate. Some vaccines can use other mammal cells or eggs, but some need human cells. During the early development of some vaccines such as the rubella and hepatitis A vaccines, human cell lines were used (view more information). These cell lines were developed in the 1960s from 2 aborted fetuses. The fetuses were not aborted for the purpose of developing vaccines or for any particular scientific reason. The cell lines MRC-5 and WI-38 were frequently used for the development of vaccines. There has been no new fetal cells required in the ongoing production of vaccines nor is there fetal tissue in vaccines. As with all viral vaccines, multiple purification steps ensure that cells are not in the final vaccine product. You cannot get someone’s DNA from vaccines. Advances in vaccine technology such as the mRNA vaccines, has reduced the need to use cell lines in recent years.

The rubella vaccine now helps prevent abortions. Prior to the vaccine in the early 1960’s there were approximately 20,000 infants born with rubella related congenital defects, 6,000 spontaneous abortions and 5,000 induced abortions.


History of Vaccines website provides more about human cell lines or strains and their use in vaccines.
The Immortal Life of Henrietta Lacks Read about Henrietta, the science, the scandal, and her amazing immortal cell line.


Now we come to probably the most contentious ingredient of all. Why are we still talking about thimerosal, you might wonder, when it isn’t even in any childhood vaccines? That’s right. Thimerosal is only added as an ingredient in multi-dose flu vaccines as a preservative to prevent contamination and growth of potentially harmful bacteria. Many pediatricians carry thimerosal-free flu vaccines and understand your concern in asking for them.

Although thimerosal was removed from vaccines in 1999 as a precautionary action, there was never any scientific evidence that thimerosal caused harm. This cautionary action has backfired on vaccine advocators. The removal of thimerosal was seen as an admission that vaccine ingredients have dangerous outcomes such as contributing to autism rate increases. Of course, autism rates appear to still be increasing despite thimerosal no longer being used routinely.

Because the concern was so great among parents both here and in Europe, many people chose not to have their children vaccinated for measles. This led to large and substantial outbreaks of measles that are still going on in Europe.

Ethyl and Methyl Mercury

Much of the confusion around thimerosal stems from the confusion of the different types of mercury. (How’s that chemistry degree coming, right?) There are so many well-written web pages about the difference between the mercury used in vaccines (ethyl) and the dangerous mercury often found in the environment (methyl) that we won’t go into it here. However, we recommend the CDC’s Thimerosal page for a discussion on the topic and a list of resources.


CDC list of research papers


(Note: Some are embedded within the paragraphs.)

National Network for Immunization Information: Aluminum Adjuvants in Vaccines.
USFDA: Vaccines, Blood & Biologics: Study Reports Aluminum in Vaccines Poses Extremely Low Risk to Infants.
Updated aluminum pharmacokinetics following infant exposures through diet and vaccination (PDF).
Keith LS, Jones DE, and Chou C-HAJ (2002). Aluminum toxicokinetics regarding infant diet and vaccinations. Vaccine, 20:  S13-17.
Jefferson T, Rudin M, and Di Pietrantonj C (2004). Adverse events after immunisation with aluminium-containing DTP vaccines: systematic review of the evidence. The Lancet Infectious Diseases,  4(2):84-90.