Why Do Pertussis Vaccines Fail?

Abstract

* Abbreviations: DTaP — : pediatric diphtheria and tetanus toxoids and acellular pertussis vaccine DTP — : pediatric diphtheria and tetanus toxoids and whole-cell pertussis vaccine FHA — : filamentous hemagglutinin FIM — : fimbriae PCR — : polymerase chain reaction PRN — : pertactin PT — : pertussis toxin WHO — : World Health Organization During the 2010 pertussis epidemic in California, there was considerable concern in the press and in public health communications about the possible contribution of vaccine failures to the problem.1,2 In this commentary, I examine why pertussis vaccines fail and Table 1 lists 8 possible reasons. View this table: TABLE 1 Possible Reasons Why DTP, DTaP, and Adolescent- and Adult-Formulated Tetanus and Diphtheria Toxoids and Acellular Pertussis Vaccines Fail The first reason, and perhaps the most important one, is that our estimates of vaccine efficacy have been inflated because of case definition.3–11 At the time of the pediatric diphtheria and tetanus toxoids and acellular pertussis (DTaP) vaccine efficacy trials in the early 1990s, it was hoped that a universal case definition could be developed so that the results of the various trials could be compared. To this end, the World Health Organization (WHO) case definition was developed.3 The primary case definition required laboratory confirmation and ≥21 days of paroxysmal cough. I was a member of the WHO committee and disagreed with the primary case definition because it was clear at that time that this definition would eliminate a substantial number of cases and therefore inflate reported efficacy values.4–11 Nevertheless, the Center for Biologics Evaluation and Research of the Food and Drug Administration accepted this definition, and package inserts of the US-licensed DTaP vaccines reflect this. For example, Infanrix (containing 25 μg pertussis toxin [PT], 25 μg filamentous hemagglutinin [FHA], and 8 μg pertactin [PRN]) and Daptacel (containing 10 μg PT, 5 μg FHA, 5 μg fimbriae [FIM]-2/3, and 3 μg … Address correspondence to James D. Cherry, MD, MSc, Department of Pediatrics, David Geffen School of Medicine at UCLA, 10833 Le Conte Ave, MDCC 22-442, Los Angeles, CA 90095-1752. E-mail: jcherry{at}mednet.ucla.edu