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Biosecurity Briefing
Study Supporting CDC Flu Guidance Questioned By Jennifer Nuzzo, November 30, 2007 Commentaries written recently by pandemic flu historian John Barry and infectious diseases expert Michael Osterholm raise serious questions about the validity of results published in a Journal of the American Medical Association (JAMA) study that “now serves as the core support for the recent Centers for Disease Control and Prevention [CDC] recommendations for the use of community mitigation strategies…during a[n influenza] pandemic.”1 The study in question is a historical analysis of the efficacy of nonpharmaceutical interventions (NPIs) used by public health authorities to control the spread of disease during the 1918 epidemic.2 The study was conducted by a team including University of Michigian historian Howard Markel and Martin Cetron of the U.S. Centers for Disease Control and Prevention, the agency which supported the study. Markel et al examined the “public health actions taken in 43 cities during the 1918-19 pandemic and the associated morbidity and mortality in those cites…and [they] concluded that when NPI strategies were employed, they made a difference.”1 As a specific example the study pointed to the effects seen in New York City, which “mounted an early and sustained response to the epidemic and experienced the lowest death rate on the Eastern seaboard.”2 Following publication of the findings, historian John Barry of Tulane University conducted his own examination of the historical record in two of the cities (New York and Chicago) examined by Markel et al. His findings were published in short-version in JAMA as a letter to the editor3; a lengthier analysis was subsequently published on the Center for Infectious Disease Research & Policy (CIDRAP) website1. Barry found evidence suggesting that NPIs were not implemented by these cities as the study authors reported. In his brief reply published in JAMA, Barry noted that he found no evidence that “New York City ever took any action that meets the authors' definition of a nonpharmaceutical intervention: school closure, cancellation of public gatherings, and isolation and quarantine” and suggested that his assessment of the “events in New York City do not support the authors' hypothesis and may even refute it.”3 In the case of Chicago, Barry found evidence that Chicago implemented a fewer number of NPIs than indicated in Markel and Cetron’s study.1 In an “authors’ reply” published in JAMA alongside Barry’s short letter to the editors, Markel et al write that they “strongly disagree with Mr. Barry’s claims” that their study suffers from methodological and data quality problems.4 In particular, they “cited news reports from the New York Times and JAMA as evidence that the city [of New York] did use isolation and quarantine.”1 In addition to Barry’s lengthier analysis, CIDRAP published commentary by CIDRAP Director Michael Osterholm analyzing Barry’s evidence and the authors’ reply., Dr. Osterholm believes that Markel et al still have not addressed “the important challenges that Barry presented. In my view, his information raises serious challenges to the scientific integrity of what Markel and colleagues have reported for two cites included in their study, which in turn raises important questions about the overall results of their study. This concern does not disprove that NPIs altered the course of the pandemic. But we in public health will face overwhelming challenges with risk communication and credibility during the next pandemic. While we will surely recommend the use of NPIs at that time, we have an obligation to society to tell exactly what we know and explain the science that supports our conclusions….I believe John Barry makes a clear and compelling case. . .that Markel has not met that standard. We must.”1 References
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