PIP: Vaccination is the only method of proven effectiveness for the control of whooping cough. Although effective, the vaccine is associated with a high rate of side effects, including local soreness, mild systemic reactions (fever), and occasionally neurologic reactions. Despite these reactions, there is general agreement that the benefits of pertussis vaccination outweigh these risks. With the decline in the incidence of pertussis, however, there is concern that the use of the vaccine may constitute a greater risk than the disease and some have challenged the continuation of routine vaccination. Experience in the UK suggests that this would not be a wise strategy. As a result of reports in the media linking pertussis vaccine with brain damage, the acceptance levels in England for this vaccine fell from 79% in 1973 to 31% in 1978, resulting in a pertussis epidemic beginning in 1977. Applying these data to the US would mean about 10,000 cases of pertussis could be expected per week during a similar epidemic. The risk of persistent neurologic damage 1 year after pertussis vaccination has been estimated at 1/310,000 immunizations. The reaction rate with pertussis vaccine is higher than that exhibited by other widely used vacciness; there have been no significant changes in the vaccine since its formulaltion in 1940. Modern technology should facilitate the development of an effective pertussis vaccine with fewer side effects. Recent host-parasite interaction studies and analyses of the immunoche,ostru pf Bordetella pertussis have identified 2 potential immunogens that are candidates for inclusion in a new acellular vaccine. New vaccines probably will contain lymphocytosis-promotiong toxin, filamentous hamagglutinin, and greatly reduced levels of endotoxin . Until a safer vaccine is avilable, active pertussis immunization programs should be continued to prevent a resurgence in whooing cough.