Transmission of Bordetella pertussis to young infants. Pediatr Infect Dis J

Baylor College of Medicine, Houston, Texas, United States
The Pediatric Infectious Disease Journal (Impact Factor: 2.72). 04/2007; 26(4):293-9. DOI: 10.1097/01.inf.0000258699.64164.6d
Source: PubMed


Pertussis vaccination has reduced the number of notified cases in industrialized countries from peak years by more than 95%. The effect of recently recommended adult and adolescent vaccination strategies on infant pertussis depends, in part, on the proportion of infants infected by adults and adolescents. This proportion, however, remains unclear, because studies have not been able to determine the source case for 47%-60% of infant cases.
A prospective international multicenter study was conducted of laboratory confirmed infant pertussis cases (aged <or=6 months) and their household and nonhousehold contacts. Comprehensive diagnostic evaluation (including PCR and serology) was performed on all participants independent of symptoms. Source cases were identified and described by relationship to the infant, age and household status.
The study population comprised 95 index cases and 404 contacts. The source of pertussis was identified for 48% of infants in the primary analysis and up to 78% in sensitivity analyses. In the primary analysis, parents accounted for 55% of source cases, followed by siblings (16%), aunts/uncles (10%), friends/cousins (10%), grandparents (6%) and part-time caretakers (2%). The distribution of source cases was robust to sensitivity analyses.
This study provides solid evidence that among infants for whom a source case was identified, household members were responsible for 76%-83% of transmission of Bordetella pertussis to this high-risk group. Vaccination of adolescents and adults in close contact with young infants may thus eliminate a substantial proportion of infant pertussis if high coverage rates can be achieved.

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Available from: Flor M Munoz
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    • "In older children, adolescents and adults, pertussis typically causes a prolonged cough illness which may be associated with complications and a substantial economic cost [3] [4]. Older age groups are the primary source of pertussis transmission to infants who are at greatest risk of severe pertussis disease and death [5] [6] [7]. "
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    • "Although vaccination of infants over the first 18 months of life is common in many countries, including Mexico, there is still a window of time before vaccination can produce its full effect. During this period, newborns are vulnerable if they come in contact with infected people who are actively shedding bacteria (Wendelboe et al., 2007). Even in a country with long-standing universal childhood vaccination, waning immunity makes adolescents and adults susceptible to reinfections with subclinical disease who then become carriers and transmitters of the bacteria. "
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    • "The lower test positivity rate in infants and young children in sporadic setting could be due to over sampling, which suggested that the disease burden in adolescent and young adults were underestimated in Alberta with their high test positivity rate. One extensive case-based study found that household contacts were the cause of 48-55% of B. pertussis transmission to the <1 year age group, which support the importance of disease control and prevention in adolescents and adults [33]. The severity of pertussis in young infants was shown in a study in 25 pediatric intensive care units in United Stated where 83% of the 124 critical cases were younger than 3 months old and had a 10% mortality rate [34]. "
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