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Pertussis now passes most commonly from siblings to infants
According to recently published data, the most common source of pertussis transmission in the United States has shifted from mother to child and now occurs primarily between siblings.
“Our analysis of U.S. Enhanced Pertussis Surveillance data revealed a shift in the source of infant pertussis infection from mothers to siblings, mirroring the shifting epidemiology of pertussis in the United States,” Noelle Cocoros, DSc, MPH, of the department of population medicine at Harvard Medical School, and colleagues wrote “With evidence of waning immunity and possible transmission of pertussis through subclinical infections, the current cocooning strategy is unlikely to offer sufficient protection of vulnerable infants.”
The researchers identified 1,306 cases of pertussis in children aged younger than 1 year via Enhanced Pertussis Surveillance sites nationwide between 2006 and 2013. Source of infection information was obtained through interviews with parents of the infected children.
Results showed a source of pertussis infection was identified for 569 children. Infants aged younger than 1 month were more likely to have a source of infection identified than older children (P < .0001). Sources of pertussis infection were most commonly a family member, making up 66.1% of identified sources. Researchers found that pertussis was most likely to be transmitted by a sibling in 35.5% of cases, while transmission came via mothers in 20.6% of cases. This shift began in 2008, according to the researchers.
Data also showed that about 24.2% of pertussis cases occurred in children aged younger than 2 months. By sex, pertussis cases by sex were nearly identical: 50.5% in boys vs. 49.5% in girls.
The researchers emphasized the need to vaccinate children against pertussis, via maternal vaccination, due to unavoidable close contact between infants and family members.
“Prevention efforts should therefore focus on increasing Tdap coverage during pregnancy because this is currently our best strategy for providing direct protection to the infant, regardless of the changing source of infant infection,” Cocoros and colleagues wrote. – by David Costill
Disclosure: The researchers report no relevant financial disclosures.
