JAMA and Slate on vaccine-related replacement disease

A common question asked about vaccines that target specific variants of a pathogen (such as HPV, pneumococcus, or meningococcus) is how great the likelihood is that 'replacement disease' may occur. Simply stated, this phenomenon describes the emergence of new serotypes or subtypes not included in a vaccine becoming more prevalent as those that are included in the vaccine are eliminated.

A paper in JAMA this spring suggested replacement disease may be occurring among recipients of Prevnar, Wyeth's pneumococcal conjugate vaccine. (Four doses of the vaccine are recommended for all U.S. infants.) The paper was the basis for a commentary by Arthur Allen ("Fear of Replacement: What if a vaccine kills off one strain of a disease—but makes room for another?") that appeared in Slate late last month.

Ben Kleifgen, working at the Penn Center for Bioethics this summer, summarizes both items:

"In the JAMA paper, CDC’s Arctic Investigations Program observed an increase in pneumococcal infections in Native Alaskans receiving Prevnar. Of particular concern to researchers is the fact that the infections are largely from serotype 19A, a highly virulent but previously quite rare strain. Allen wonders if the threat of replacement disease may discourage further vaccine development, although the situation may not be that bleak. There is evidence that the new strain may be on the rise worldwide, unrelated to the use of Prevnar. In addition, Wyeth and GSK are both working on new pneumococcal vaccines that will cover 19A."