Should the Topic of Thimerosal-Free Vaccines Be Discussed With Parents if They Don't Ask About It?

PRO: With the sole exception of the multidose influenza vaccine, childhood vaccines are now thimerosal-free. Communicating this fact (with signs in clinic) is a quick and effective way of making this concern a non-issue. It helps reinforce the message that vaccines are safe. Parents are made aware that the pediatrician is cognizant of their concerns and has endeavored to address those concerns.

Adverse effects of vaccines, both real and perceived, are a significant barrier to vaccine acceptance. Parents have become more skeptical about the risks and benefits of vaccines. This is especially relevant now that parents are less exposed to the diseases that vaccines prevent and are more aware of the potential adverse effects of vaccines. Parents may not always verbalize their concerns to the provider. It helps to let parents know that they are not exposing their child to increasing amounts of a potential neurotoxin by agreeing to more vaccinations.

The issue of thimerosal in vaccines and the potential risk to the developing brain of infants and children has received wide attention in the media. Organic mercuric compounds are known to be toxic, and the public is becoming aware that even small doses of these compounds may not be safe. In 1994, the Environmental Protection Agency recommended that the allowable level for methylmercury be decreased from 0.3 µg/kg to 0.1 µg/kg. However, thimerosal is metabolized to ethylmercury and is excreted rapidly. The CDC has not established safe levels for this form of mercury. Studies to date have not shown harmful effects from these compounds or thimerosal at the doses present in vaccines.¹ However, these finer technical details are not widely known, even by medical professionals.

That the risk of thimerosal is more theoretical rather than actual is a moot point. Its removal from vaccines has legitimized the risk in the minds of parents.² Now that the specter has been raised, it is best to effectively bury it by advertising to parents that their child's vaccines are free of thimerosal.

SHIV SOMESHWAR, MD
Dr Someshwar is associate professor and chief of the division of general pediatrics and medical director of the Pediatric Group Practice & Hospitalist Service at West Virginia University School of Medicine in Morgantown.

REFERENCES:
1. US Food and Drug Administration. Thimerosal in vaccines questions and answers. http://www.fda.gov/BiologicsBloodVaccines/vaccines/QuestionsaboutVaccines/ucm070430.htm. Accessed August 10, 2010.
2. Offit PA. Thimerosal and vaccines—a cautionary tale. N Engl J Med. 2007;357:1278-1279.

CON: Pediatricians should not post signs or advertise that their vaccines are thimerosal-free. If the physician finds credibility in the multiple studies and major medical agencies that have refuted the thimerosal–neurodevelopmental disorders link, then there is no need to proclaim that the vaccines are thimerosal-free. The science does not support the concern in the first place.¹

Psychological research, as described by Schwarz and colleagues,² has found that the repetition of false information—even if it is refuted—can contribute to the future acceptance of the false information. Furthermore, when the false information is introduced by a trusted, reliable source, such as a physician (again, even when it is being refuted), it is more likely to be remembered and possibly believed in the future.

Certainly, if a parent asks about the alleged thimerosal–neurodevelopmental disorder link because a relative or friend mentioned it or because he or she read something about it on the Internet, then a thorough explanation has to be provided. Once a parent inquires about any of the vaccine controversies, the specific controversy should be discussed early and often so that misconceptions are not established in the parent's mind.³

For the parent who does not have such questions, however, the unsolicited proclamation by the pediatrician that "this clinic's vaccines do not contain thimerosal" (either verbally or in a poster on the wall) turns this non-issue into an issue of major importance—just as recurrent, inaccurate media messages do.³

Furthermore, the pediatrician already has to spend several minutes describing the proven potential adverse effects of vaccines and does not have the time to mention theoretical risks, especially those that have already been refuted with sound scientific study.

LINDA S. NIELD, MD
Dr Nield is associate professor of pediatrics at West Virginia University School of Medicine in Morgantown.

REFERENCES:
1. Nield LS. Vaccine "scares": update on thimerosal. Consultant for Pediatricians. 2006;5(10 suppl):S9-S12.
2. Schwarz N, Sanna LJ, Skurnik I, Yoon C. Metacognitive experiences and the intracacies of setting people straight: implications for debiasing and public information campaigns. Adv Exp Soc Psychol. 2007;39:127-161.
3. Nield LS. Anti-vaccine media: its impact—and strategies to combat it. Consultant for Pediatricians. 2008;7(9 suppl):S4-S7.