Increase in deaths from pertussis among young infants in the United States in the 1990s

Background. Severe pertussis primarily occurs among infants (<12 months of age). Despite high levels of immunization, reported pertussis cases increased in the United States in the 1990s among all age groups, including infants. Methods. To characterize fatal pertussis cases, we analyzed pertussis deaths reported to CDC in the 1990s and compared these with data on pertussis deaths reported in the 1980s. Data from national surveillance systems and from available medical records were used, including data from analyses of deaths reported in 1992 through 1995. Results. In 1980 through 1989, 77 pertussis deaths were reported; 61 deaths were among infants (1.67 deaths per million), including 49 among infants <4 months of age. In the 1990s 103 pertussis deaths were reported; 93 deaths were among infants (2.40 deaths per million), including 84 among infants <4 months of age. Of 89 infants with ethnicity data, 31 (36%) were Hispanic; the mortality rate among Hispanic infants (4.77 per million) was higher than among non-Hispanic infants (1.80 per million). Of 76 infants with reported gestational age, 40 (53%) were born at <37 weeks, including 22 (29%) who were born at <35 weeks. Severe pulmonary hypertension was a common lethal complication among infants. Conclusions. Pertussis deaths increased among infants too young to be protected by immunization. A disproportionate share of deaths were complicated by pulmonary hypertension and occurred among Hispanic infants and infants born at <37 weeks gestation. New approaches to prevent infection among infants <4 months of age and improved therapies for pertussis complications are needed.