The objective of a vaccine for pertussis is to prevent the paroxysmal cough with its complications. Prevention of the paroxysmal cough should prevent transmission of B. pertussis. Clinical studies indicate that a critical level of antitoxin confers protection against pertussis and that the long-lived protective immunity that follows pertussis is best explained by the presence of antitoxin. Vaccine-induced protective immunity can be mediated by a critical level of antitoxin alone. In addition to preventing pertussis with vaccines, we predict this level of antitoxin will also exert epidemiologic control (herd immunity) by inhibition of colonization with B. pertussis and by prevention of the paroxysmal cough which will reduce transmission of this pathogen. Lastly, a pertussis toxoid need not have detectable pharmacologic activity to exert its protective actions: residual activity could exert a deleterious effect on glucose metabolism and exert immunomodulating effects. Accordingly the new pertussis vaccine should contain inactivated pertussis toxoid alone and there is no need to include other components. Several candidates could serve as a satisfactory pertussis toxoid. The admonition to physicians given by Hippocrates, Primum non nocere (first of all do no harm), should be heeded by those responsible for the development and use of the new pertussis vaccine.