Adjuvants, substances that enhance the immune response to vaccine antigens, are discussed in detail in Chapter 1: Introduction to Vaccinology—Basic Vaccine Immunology. Aluminum salts have been used as adjuvants for over 80 years, and hundreds of millions of people have received vaccines containing them. Whereas local reactions such as erythema, nodules, hypersensitivity, and granuloma formation have been reported, serious or persistent adverse events have not.
A meta-analysis published in 2004 included studies that compared alum-adjuvanted DTP vaccines to their nonadjuvanted counterparts. In children ≤18 months of age, vaccines containing aluminum hydroxide caused nearly twice as much erythema and induration but there was no increase in collapse, convulsions, or persistent screaming or crying. In older children, aluminum-containing vaccines caused more localized, persistent pain, but not erythema, induration or fever. In some sense, the pain is part of the gain—the irritation or inflammation (and hence pain) caused by the adjuvant also drives the immune response.
Large quantities of aluminum can cause neurologic disease. However, the burden of aluminum exposure through vaccines is far less than the guidelines for safe exposure established by the Agency for Toxic Substances Disease Registry. In fact, infants are exposed to much more aluminum through their diets than through vaccines. Whereas the total aluminum exposure from vaccines in the first 6 months of life is <5mg, breast-fed infants ingest 7mg and formula-fed infants as much as 38 to 117mg over the same period of time, depending on the type of formula.
The newest adjuvant on the block, AS04 (used in HPV2), contains a derivative of lipopolysaccharide, a major component of bacterial cell walls. Parents may cite this when they say that vaccines “contain toxins”. However, they need to understand that exposures to toxins like lipopolysaccharide occur continuously given our symbiotic relationship with bacteria.
The truth is that anything (even water!) can be dangerous if taken in large amounts. The amount of lipopolysaccharide in AS04-adjuvanted vaccines is just enough to stimulate a robust antibody response but not nearly enough to cause major problems. This is borne out by many studies demonstrating excellent tolerability and no association with serious adverse events. Even more insidious events have been carefully studied; for example, in an integrated analysis of randomized controlled trials involving nearly 70,000 vaccinees, autoimmune events occurred in about 0.5% of both AS04-exposed and nonexposed individuals after a mean follow-up period of 21 months.
—Marshall, Gary S. “Addressing Concerns About Vaccines.” The Vaccine Handbook: A Practical Guide for Clinicians. 3rd ed. New York: Professional Communications, Inc., 2010. 212-213. Print.