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This fall's outbreak of pertussis in Iowa has focused statewide attention on whooping (which, incidentally, is pronounced "hooping") cough. Although this disease is well documented in older pediatric textbooks, today we seem to recall little about its epidemiology. Whooping cough was very common in the US before World War II. Epidemics were spread by grade school children, who brought the disease home to their younger siblings. Only children younger than age one were at high risk from pertussis, which for them could be deadly. Immunity after natural infection was thought to be lifelong. Immunization with whole cell pertussis vaccine was begun in the 1940s to interrupt the annual epidemics and prevent death in the very young. Death rates for infants could reach 1:100 and higher, so the vaccine was widely accepted. When universal vaccination was achieved, the epidemics abated and death from pertussis became a rare event. But physicians and parents began to note that whole cell pertussis vaccine occasionally caused severe side effects, including seizures and encephalopathy. Through the 1970s the debate continued regarding the risks and benefits of this vaccine. Extensive analysis suggested a rate of one severe complication per 300,000 immunizations. Even so, numerous litigations ensued; most manufacturers of pertussis vaccine withdrew their products, and the search began for an improved, less reactogenic vaccine. The resulting acellular pertussis vaccine is now approved for infants, and is given in combination with diphtheria and tetanus toxoids at 2, 4, and 6 months, at 15-18 months, and at 4-6 years. The rate of serious complications with the acellular vaccine is certainly less than that of the whole cell vaccine. Acellular pertussis vaccine is not approved for administration to children older than 6 years. However, during the recent outbreak in Iowa, we have suggested that children through the first grade (or age 7) receive their final acellular pertussis booster if they have not had any pertussis booster since the age of 18 months. The antibiotic of choice for treatment of whooping cough is erythromycin estolate (Ilosone) at a daily dosage of 40 mg per kg, divided TID. An adequate length of therapy is 14 days. For older children who cannot tolerate erythromycin, the alternative is Biaxin (Abbott), at a daily dosage of 15 mg per kg, divided BID. Erythromycin is not typically prescribed for adolescents and young adults because gastrointestinal side effects are so common; instead, give Biaxin at 500 mg BID for 14 days. |
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