Although rare in the U.S., infant deaths due pertussis, also known as "whopping cough," could be further reduced by focusing on certain risk factors, according to a report from researchers with the Centers for Disease Control and Prevention in Atlanta.

The highest rates of pertussis deaths occur in infants younger than 12 months old who are too young to be vaccinated, Dana L. Haberling and colleagues note in the current issue of The Pediatric Infectious Disease Journal. Pertussis is a highly contagious disease caused by the bacterium Bordetella pertussis, which can lead to pneumonia, middle ear infection, loss of appetite, sleep disturbance, dehydration, seizures and even death.

The team used the U.S. Multiple Cause-of-Death and Linked Birth/Infant Death databases between 1999-2004 to examine pertussis-related infant deaths and to explore the possible causes or common features of the deaths.

There were 91 infant deaths during this period. All occurred in infants younger than 7 months of age, and 53 deaths, or 58 percent, occurred in infants younger than 2 months of age.

The average annual infant mortality rate attributed to pertussis was 3.8 deaths per million live births for all infants younger than 1 year of age, and 13.1 deaths per million live births for all infants younger than 2 months of age.

The investigators found an independent association between infant deaths from pertussis and birthweight below 2500 grams, female sex, an Apgar score below 8 and a mother with less than 12 years of education.

The mortality rate among Hispanic infants less than 2 months of age was 2.6 times greater than non-Hispanic infants of the same age.

"Although our findings do not suggest a causal relationship between specific infant or maternal characteristics and infant pertussis-related deaths, these indicators of high risk should be given consideration when implementing strategies to prevent pertussis and infant pertussis deaths," Haberling and colleagues write.

They note that a tetanus/diphtheria/pertussis booster is recommended for adults and adolescents. "Ensuring pertussis booster vaccination of adults and adolescents in close contact with an infant is warranted to prevent transmission of pertussis to vulnerable infants, particularly infants too young to be immunized," the investigators advise.