Balancing Risks and Benefits: Primum non nocereIs Too Simplistic

The commentary by Seal and Daum entitled “What Happened to Primum non nocere?” 1 that appeared in the May 2001 issue of Pediatrics criticized the July 1999 recommendation of the American Academy of Pediatrics (AAP) and US Public Health Service (USPHS) to delay the birth dose of hepatitis B vaccine for infants born to hepatitis B surface antigen (HBsAg)-negative women to reduce infant exposure to thimerosal.2 The commentary contains incorrect statements and oversimplifies the complex process of balancing multiple risks and benefits when formulating vaccine policy as summarized in the excellent article by Feudtner and Marcuse3 in the same issue. Some professionals had difficulty understanding the need for the July 1999 recommendations because they didn't fully understand the risks from organomercury exposure and the amounts of ethylmercury present in vaccines. Several developments in the past 2 years have reinforced the wisdom of the recommendations made in July 1999. Seal and Daum stated that methylmercury “might” be harmful to the developing fetal central nervous system. Methylmercury is neurotoxic at all ages, and the developing fetal brain is at least 10-fold more sensitive than the adult brain.4 They also incorrectly stated that “no data existed that implicated ethylmercury” as a cause of neurotoxicity. As reviewed by Ball et al,5 ethylmercury from thimerosal has caused significant neurotoxicity in infants, children, and adults. Such data were available at …