762. Increased Risk for Pertussis at 7-10 Years is Associated with Younger Age at 4-6 Year Old Booster DTaP
Session: Oral Abstract Session: Pertussis Vaccines and Challenges
Friday, October 21, 2011: 2:30 PM
Room: 156ABC
Background:  Despite high vaccination rates, pertussis has been increasing in incidence since the beginning of the millennium, as a result of waning immunity in the adolescent and adult age groups.  To reduce the adolescent and adult burden of pertussis, Tdap booster was recommended in 2006 for persons 11 years and older.  However, since 2008, pertussis incidence has continued to increase in the US with the highest number of cases among children aged 7-10 years.

Methods:  A retrospective cohort was created by linking pertussis reports of children aged 7-11 years in Philadelphia to immunization registry data for their birth cohort (births between July 1, 1993 and December 31, 2000).  The cohort was limited to individuals with documented DTaP receipt between 4 and 6 years of age. Pertussis cases were restricted to those meeting the CDC case definition of a confirmed or probable case. Association between age at most recent DTaP dose between 4 and 6 years of age and risk of pertussis between 7 and 11 years of age was assessed.

Results:  Of 103,986 children in the cohort, 43 had pertussis reported between 7 and 11 years of age (41 cases per 100,000 population).  Of cases, 42 were clinical- and 1 was culture-confirmed.  The median age at last DTaP was 4.5 years for the entire cohort.  Among the cases, the median age at pertussis was 10.2 years and the median time from last DTaP to pertussis was 5.2 years.  For pertussis cases, 79% received their last DTaP at 4 years of age compared with 70% for those who did not have pertussis.  Children who received DTaP booster at 4 years of age were 1.6 times more likely to have pertussis between 7-11 years of age than children who received DTaP booster at 5 or 6 years of age.

Conclusion: Even in a very limited window of risk (5 years), children who received their last childhood DTaP vaccination at an earlier age tended to be at increased risk for pertussis. This increased risk for pertussis in 7-11 year old children is likely due to waning immunity, which could be minimized through administration of DTaP closer to 6 years of age rather than at 4 years of age.

Subject Category: I. Adult and Pediatric Vaccines

Irini Daskalaki, MD1,2,3, Liyuan Ma, MS1, Claire Newbern, PhD, MPH1, Kendra Viner, PhD, MPH1, Sarah Long, MD4 and Caroline C. Johnson, MD5, (1)Philadelphia Department of Public Health, Division of Disease Control, Philadelphia, PA, (2)Drexel University College of Medicine, Philadelphia, PA, (3)St Christopher's Hospital for Children (SCHC), Philadelphia, PA, (4)St Christopher's Hospital for Children (SCHC), Drexel University College of Medicine, Philadelphia, PA, (5)Division of Disease Control, Philadelphia Department of Public Health, Philadelphia, PA


I. Daskalaki, None

L. Ma, None

C. Newbern, None

K. Viner, None

S. Long, None

C. C. Johnson, None

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