Fatalities from pertussis on the rise among U.S. infants

Majority of deaths from pertussis during 2000 to 2005 occurred among infants aged younger than 1 year.

Issue: June 2008

The researchers from the National Center for Immunization and Respiratory Diseases identified a gradual, increasing trend in reported fatal cases of pertussis among U.S. infants between 2000 and 2005.

“Fatal pertussis occurred predominantly among infants who were too young to be vaccinated with even one dose of diphtheria and tetanus toxoids and acellular pertussis vaccine and less commonly among inadequately vaccinated infants aged younger than 6 months,” Tejpratap S.P. Tiwari, MD, of the Division of Bacterial Disease at the NCIRD, told Infectious Diseases in Children. “For the majority of fatal infant cases, the source for infection was a parent, sibling, grandparent or household member.”

Tiwari presented findings on data collected on fatal pertussis cases reported in the United States from 2000 to 2005 at the 42nd National Immunization Conference, held in Atlanta in March.

Surveillance system data

The researchers collected data on fatal pertussis cases reported to the National Notifiable Diseases Surveillance System from 2000 to 2005. Additional data were obtained from case report forms and medical records such as hospital discharge summaries, death certificates and autopsy reports.

Tiwari and colleagues identified 140 pertussis-related deaths from 2000 to 2005 compared with 103 from 1990 to 1999.

Overall, more deaths occurred among girls (54%) than boys (46%) from 2000 to 2005. Ethnicity data were recorded for 123 of the fatal cases, and 49% of fatalities occurred among Hispanic infants. The mortality rate for Hispanic infants was higher than in the non-Hispanic population.

According to Tiwari, most deaths occurred among infants aged younger than 1 year (n=131); 126 occurred among infants aged younger than 4 months; and six deaths occurred among patients aged older than 7 years.

Reported complications included:

Pneumonia: 92%.
Pulmonary hypertension: 35%.
Coinfections: 30%.
Seizures: 7%.
Encephalopathy: 5%.

The data further indicated that 97% of the fatalities occurred among children who were not vaccinated and 2% occurred among those who received more than one dose of the vaccine.

An identifiable source of infection was reported for 73 of the 131 infants aged younger than 1 year. A parent, sibling or grandparent had an antecedent cough-illness in the household of 89% of the 73 infants.

“A tetanus-diphtheria-pertussis vaccine (TdaP) should be given to parents of newborns and other household members who are aged 11 to 64 years and who have never received a dose of TdaP to protect newborns who are too young to be vaccinated against pertussis,” Tiwari said. “Similarly, TdaP should be given to people who are or who anticipate being in contact with newborns or infants who have not completed their primary series of DTaP, such as health care workers, adolescent or adult babysitters or daycare providers.”

According to the researchers, further studies are needed to evaluate the risk factors for fatal pertussis.

“Pediatricians should educate parents to avoid exposing newborn infants to people with even mild respiratory illness to prevent possible pertussis infection. Unimmunized infants can develop severe or fatal disease after exposure to a pertussis case,” Tiwari said. “In an outbreak situation or in communities with increased pertussis activity, pediatricians may consider using an accelerated DTaP schedule and administer the first dose of DTaP vaccine at age 6 weeks instead of the routinely recommended age of 2 months.” – by Jennifer Southall

For more information:

Tiwari T. Reported pertussis-related deaths to the National Notifiable Diseases Surveillance system and the CDC in the United States, 2000-2005. #82. Presented at: the 42nd National Immunization Conference; March 17-20, 2008; Atlanta.