Pertussis: old foe, persistent problem.

Although a safe and effective vaccine is available, pertussis continues to be an important cause of morbidity and mortality. Immunity acquired from natural infection or vaccination wanes within 5 years, making older children, adolescents, and adults important reservoirs of infection. Many neonates and infants contract pertussis from older people with mild symptoms and are at risk for developing severe, life-threatening illness. Immunization programs are being considered for adolescents and for adults who live with or care for infants.