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Siblings Now Most Likely Source of Pertussis Infection Among Infants

Historically, mothers have been identified as the most common source of pertussis transmission to infants, but a new study shows that siblings are now more likely to pass along the bacteria to infants. The study, “Sources of Infant Pertussis Infection in the United States,” appearing in the October 2015 Pediatrics (published online Sept. 30), identified 1,306 cases of infant pertussis between 2006 and 2013 and determined that immediate family members were the source of infection 66.1 percent of the time. Overall, the study identified siblings as the source of infection 35.5 percent of the time.  In contrast, mothers were found to be the source of infection in 20.6 percent of infant cases, and fathers in 10.0 percent of infant cases.  Study authors said the shifting source of infant pertussis infection from mothers to siblings mirrors the evolving epidemiology of pertussis in the United States, with evidence of waning immunity from pertussis vaccines among children and adolescents. The primary focus of pertussis prevention and control strategies is to protect those at highest risk for severe pertussis infection, particularly young infants in the first few months of life before immunizations begin.  In light of the changing epidemiology of pertussis and the shift in infant source of infection to siblings, prevention efforts should focus on increasing Tdap vaccination coverage during pregnancy to provide direct protection to young infants.

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The American Academy of Pediatrics is an organization of 64,000 primary care pediatricians, pediatric medical subspecialists and pediatric surgical specialists dedicated to the health, safety and well-being of infants, children, adolescents and young adults. (

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