Major Ingredients in Vaccines

Vaccines have prevented countless epidemics. They have been administered to millions of people worldwide. In order to maintain the safety and effectiveness of vaccines, they contain various additives, and some of these additives cause concern. Here is a list of major ingredients that may be found in vaccines. Not all of these ingredients are in all vaccines.

Immunizing agents

What makes a vaccine effective is the component that resembles a microorganism or a toxin. It educates the immune system about a potential enemy. A vaccine may use dead microorganisms or inactivated microorganisms to alert the body. Some vaccines use only parts of microbes, often of their outer coatings, to train the immune system to fight an invader. To read more about how vaccines work, click here.

Suspending fluids

The active ingredient in a vaccine is suspended in water, saline solution (salt water), or water containing protein. This adds bulk to the immunizing agent to make it into an easily measured dose.

Preservatives and stabilizers

These ingredients preserve the vaccine. They keep it from deteriorating, so that it is still effective and safe when used. Some preservatives include phenols, glycine, and 2-phenoxy-ethanol. Monosodium glutamate (MSG) helps stabilize some vaccines. So does ascorbic acid, also known as vitamin C.


Adjuvants are enhancers, designed to make a vaccine more effective. They prompt the immune system to respond more quickly and strongly to a vaccine. They can also help the immune response persist longer.

Aluminum phosphate and aluminum hydroxide are common adjuvants.


Amphotericin B, another antifungal, or an antibiotic, may be added to keep a vaccine germ free while it is transported and stored.

Formaldehyde may also be used to keep vaccines uncontaminated, and to render the bacteria in some vaccines that use live bacteria inactive.

Growth Media

Some vaccines, including ones for influenza, are grown in chicken eggs. The technical name of this growth medium is albumin, water-soluble protein. There are also vaccines grown in or containing other kinds of albumin.

Amino acids, proteins, may also be found in the growth medium. A very small amount of growth material may remain in a finished vaccine. In general, anyone who can eat eggs without ill effects can safely take a vaccine that contains egg albumin. Albumin also helps stabilize vaccines.


Thiomersal contains mercury. It is added to vaccines that are stored in multi-dose vials to prevent contamination and growth of bacteria. This prevents immunized people from getting infections along with their injection.

Every pediatric vaccine used in the United States contains either no thiomersal or minute trace amounts. This has added to the cost of immunizations, but it reassures users. Certain vaccines not in common use in children still do contain the substance, such as some snake anti-venoms.

Specific ingredients

A pharmacist or health care provider can give any concerned person the vaccine package insert. This lists the exact ingredients found in a particular vaccine. It also discusses any known adverse reactions.

There have been problems in the past for small numbers of people who received certain vaccines. However, the benefits of vaccination far outweigh the drawbacks. Since the advent of vaccination, deadly diseases such as smallpox and polio no longer arrive in devastating epidemics to destroy lives.