Prevention of pertussis.

Pertussis (whooping cough) is an acute respiratory disease caused by Bordetella pertussis. It occurs worldwide and is an important cause of morbidity and mortality in areas where immunization rates are low, particularly among children less than 1 year of age. The characteristic presentation of pertussis is paroxysmal coughing followed by a long inspiratory effort that produces the classic whoop. Lymphocytosis is frequently present. Complications include pneumonia and seizures secondary to hypoxia. The paroxysmal and convalescent stages of the illness can each last several weeks. Transmission occurs readily by respiratory droplets, and atypical or mild cases in older children and adults can be important in spread of the infection. Isolation, early erythromycin therapy, and erythromycin prophylaxis can reduce transmission, but vaccination is the primary means of control. An inactivated whole cell suspension of the bacterium has been an effective vaccine for protecting against pertussis since the 1950s, but whole cell vaccine may allow mild infections to occur and has been associated with local and systemic reactions that have eroded public acceptance. Component or acellular pertussis vaccines that are less reactogenic have been in use in Japan since 1981 and appear to be effective there. Development of an acellular preparation that is equally or more efficacious than whole cell vaccine may be possible, but clinical trials for measurement of protection against pertussis are difficult and trials with new pertussis vaccines will have to be carefully performed to avoid the controversies generated by earlier trials.