Trials Can Inform or Misinform: “The Story of Vitamin A Deficiency and Childhood Mortality”

This “case study” documents the ways in which a variety of epidemiologic studies and the data they generated (which challenged existing beliefs and public health constructs) were greeted by established “experts” in relevant fields. Just as Virchow described over a century ago, results of an initial observational study, which raised the issues, were entirely ignored. Prominent publication of a randomized clinical trial, which both supported the observational study’s associations and proved that they were causal, was greeted with intense hostility, disbelief, and rejection. Only the subsequent accrual of additional, similar RCTs slowly changed scientific opinion, especially when replications were eventually conducted by others than the original investigators. A halt was brought to this slowly changing scientific climate by the timely gathering of those involved in a week-long meeting that evaluated the quality and interpretation of all available data and discussed their relevance and validity. That many investigators had not understood the importance of the context in which their own studies had been conducted was startling, particularly regarding the two variables of greatest relevance: the study population’s baseline risk of vitamin A deficiency and mortality. Investigators of some of the best conducted studies misinterpreted their own data. The resulting 10-year effort eventually changed global health policy, but some “deniers,” without a shred of evidence to back their claims, still refuse to accept this outcome.