Infants younger than 3 months with pertussis show greater mortality risk

MEMPHIS, Tenn. — Infants aged younger than 3 months exhibited the highest morbidity and mortality from Bordetella pertussis infections, according to data presented at the St. Jude/PIDS Pediatric Infectious Diseases Research Conference.

Pertussis represents the fifth-leading cause of vaccine-preventable death in children aged younger than 5 years, predominantly occurring in low- to middle-income countries. To assess the burden of B. pertussis among infants aged younger than 1 year and evaluate outcomes of infants who were positive with pertussis, researcher Herberth G. Maldonado, MD, of the Universidad San Carlos de Guatemala, and colleagues examined nasopharyngeal swabs from infants with pertussis-like symptoms (n = 68) from November 2013 to October 2014.

PCR analysis and cultures were used to test for pertussis, and respiratory viruses were examined by immunofluorescence and PCR assays. The researchers also collected demographics, vaccinations, clinical and laboratory data and final outcomes in the cohort.

Twenty-eight percent of infants with pertussis-like symptoms were later confirmed to have pertussis, with PCR-positive culture identifying 23.5% of infants, PCR plus culture identifying 3%, as well as 1 case that was culture-positive but PCR-negative.

The researchers observed a mortality rate of 36.8% among infants, with infants aged younger than 3 months demonstrating a higher frequency of infection and higher mortality rates than those aged older than 3 months.

Infants with pertussis were coinfected with influenza A, adenovirus and parainfluenza virus-1, while infants negative for pertussis commonly exhibited infections with respiratory viruses (37%), including respiratory syncytial viruses, parainfluenza virus-3, adenoviruses, influenza A and influenza B.

“The clinical presentation of pertussis in children under 1 year of age might be nonspecific and atypical. Health workers should be alert to the possibility of pertussis in this age group,” Maldonado told Infectious Diseases in Children. “In our study, infants younger than 3 months had the highest morbidity and mortality. These children are too young to have been vaccinated or will have one dose when they acquire the infection.

“Although maternal vaccination with Tdap has proven effective in developed countries, there are no studies about efficacy and attenuation of the infant immune response to whole-cell vaccine, which is used in most Latin American countries.”

Reference:

Maldonado HG, et al. Abstract R201542. Presented at: St. Jude/PIDS Pediatric Infectious Diseases Research Conference; Feb. 20-21, 2015; Memphis, Tennessee.

Disclosure: The researchers report no relevant financial disclosures.