Pertussis Vaccine Encephalopathy-Reply

In Reply.—  The letters of Lewis, Menkes, Garbitelli, and Tilelli and Manniello all contain errors of fact and reasoning and seem to be aimed at preserving the myth of pertussis vaccine encephalopathy. Dr Menkes implies that in my assessment of the National Childhood Encephalopathy Study I focused on one set of biases. This is not true. Even though there clearly were biases that tended to exaggerate the calculated risks, the original data alone do not indicate a cause-and-effect relationship but only the redistribution of events over time.¹ If you believe that the increased number of vaccinations in cases during the 0- to 3-day period indicates a causative effect of vaccine, then by the same reasoning you must believe that the increased number of vaccinations in the controls during the rest of the observation period was protective against disease.Since after considerable study there is no epidemiologic evidence that supports