Updated: Noviembre 7, 2008
Some vaccines and other medicines contain chemicals called adjuvants to help stimulate the production of immunity against the vaccine ingredients, making the vaccine more effective.1 The word ‘adjuvant’ is derived from the Latin word ‘adjuvare’ which means ‘to help’.2 (See Vaccine Ingredients)
Aluminum salts have frequently been incorporated as adjuvants in vaccines licensed for use in the United States and elsewhere.
There are other adjuvants incorporated in vaccines licensed in other countries and there are other adjuvants used in other medications (which are not vaccines) that have been licensed in the United States. It is likely that other adjuvants will be incorporated in a number of new vaccines currently being tested for use in the United States.
Adjuvants serve to:
Studies have shown that many aluminum-containing vaccines cause higher and more prolonged antibody responses than comparable vaccines without the adjuvant. The benefit of adjuvants has usually been observed during the initial immunization series rather than with booster doses.1
There are three general types of aluminum-containing adjuvants:
The effectiveness of each salt as an adjuvant depends on the characteristics of the specific vaccine and how the manufacturer prepares the vaccine.3 To work as an adjuvant, the antigen must be adsorbed to the aluminum; that is, it is clumped with the aluminum salt to keep the antigen at the site of injection.4
Not all vaccines contain aluminum salts because an adjuvant may not have been needed, was not expected to increase the desired immune response, or was going to cause an imbalance in the immune response. For example, inactivated Polio Virus (IPV) vaccine, measles, mumps and rubella vaccine (MMR), varicella vaccine, Meningococcal conjugate (MCV4) vaccine, and influenza vaccines do not contain aluminum salts.2
The US licensed vaccines for children that contain aluminum adjuvants are3:
Aluminum is a very abundant element in our environment. It is in many foods we eat, many personal hygiene products we apply to our skin (deodorants, for example), and many medicines we ingest. Thus, all infants are exposed to aluminum in the environment. Breast milk, for example, contains approximately 40 micrograms of aluminum per liter, and infant formulas contain an average of approximately 225 micrograms of aluminum per liter.5
However, historically some individuals with kidney failure—who were exposed to large quantities of aluminum when undergoing dialysis—developed serious neurological effects.
Various government agencies establish guidelines for exposure to potentially toxic substances. These guidelines are called “minimal risk levels” —the maximum amount that one can be exposed to over time-usually on a daily basis-without expected harm.
The US Agency for Toxic Substances and Disease Registry (ATSDR) estimated these levels for infants taking into account the amount of aluminum a child would eat as well as receive by injection of vaccines. The body burden of aluminum from both sources is below the minimal risk level except transiently following vaccinations; since 50-70% of injected aluminum is excreted within 24 hours, this is believed to have no negative effect.6
Aluminum-containing vaccines have more than a 75 year record of safety around the world. Serious adverse effects attributable to the aluminum adjuvants are rare. However, local reactions such as redness, swelling and/or tenderness at the injection site are not infrequent. More severe local reactions such as large areas of swelling, sterile abscesses, subcutaneous (SC) nodules (small lumps under the skin some of which have inflammation in the tissue), and allergic responses are much less common.1
A recent review of the evidence of adverse events after exposure to aluminium-containing vaccines against diphtheria, tetanus, and pertussis (DTP), found no evidence that aluminum salts cause any serious or long-lasting adverse events.7
Many returning veterans from the 1990-1991 Persian Gulf War reported numerous health problems that they thought were related to their service in the Persian Gulf. In 1998, Congress directed the Institute of Medicine to evaluate possible associations between illness and a host of potential exposures, including anthrax and other vaccines.
The IOM Committee found that “although veterans …report significantly more symptoms of illness than soldiers of the same period who were not deployed, studies have found no cluster of symptoms that constitute a syndrome unique to Gulf War veterans”.8
There was insufficient evidence to establish an association with most exposures, including vaccines.
Macrophagic myofascitis (MMF) is a term that is used to describe some findings that have been seen microscopically in some muscle biopsies. The lesions are thought to be caused by tissue changes resulting from the normal immune response to the aluminum-adsorbed vaccine.9
The biopsy findings were originally described in a group of French adult patients who had muscle and joint aches and pains and fatigue.10 Although France is the exception, biopsies of muscle are not usually performed on muscles of the arm because that is where vaccines and other shots are often given. In addition, because muscle biopsies are quite painful, muscle biopsies are not performed on normal people—that is, there are no normal control muscle biopsies with which to compare the French patients’ biopsies.
Although the physician who first described the biopsy findings proposed that the aluminum-containing vaccines caused the symptoms in his patients10, most scientists believe that the tissue findings showed the normal response to the aluminum adjuvant; and many felt that the patients’ illnesses did not warrant the performance of a muscle biopsy.11