Increase in deaths from pertussis among young infants in the United States in the 1990s. Vitek CR, Pascual FB, Baughman AL and Murphy TV. Pediatric Infectious Diseases Journal 2003;22:628-634.
Explanatory note: Pertussis or whooping cough is a bacterial infection caused by Bordetella pertussis. Pertussis causes severe coughing spells and is most severe when it occurs early in life. After the introduction of pertussis-containing vaccines in the 1940s, the number of cases and deaths due to pertussis declined dramatically reaching a lowest point in the mid-1970s. However, increasing numbers of pertussis cases among adolescents, adults and young infants were observed during the 1980s.
What are the factors associated with whooping cough deaths?
This study sought to determine the total number of infant whooping cough deaths that occurred in the United States during the 1990s.
Researchers identified pertussis deaths reported to the Centers for Disease Control and Prevention, to state and local health departments, and from death certificates during the 1990s.
To determine characteristics of the fatal cases they reviewed the individual reports and available medical records, comparing them to data collected during the 1980s.
This study found that of 103 whooping cough deaths in the 1990s, 82% were less than 4 months of age and 91% less than 12 months. During the 1980s there were 77 cases of fatal whooping cough, 64% were less than 4 months, and 79% were less than 12 months of age. Nine of the 10 non infant cases had preexisting medical problems.
The majority of cases were unimmunized or incompletely immunized with a pertussis-containing vaccine.
The study also found that, when known, the source of exposure to someone with a cough illness was often (49%) in the home.
More than half of the fatal infant cases had been born prematurely (51% less than 37 weeks gestational age among those for whom the information was available).
Data on race and ethnicity was incomplete but suggested that a disproportionate number of fatal cases were Hispanic or Native American.
The number of deaths due to pertussis increased in the 1990s. A disproportionate number of these deaths were infants younger than four months of age—too young to have been protected by immunization.
The methods employed—in both this study and the one reporting cases from the 1980s—likely under reported the total number of deaths caused by pertussis.
In addition to increasing pertussis immunization levels for all children, new strategies are needed to prevent infection in very young infants.