764. Rapid Rise of Incidence Rates of Pertussis in the Five Years Following Complete DTaP Vaccination: Is Immunity Waning Earlier than Expected?
Session: Oral Abstract Session: Pertussis Vaccines and Challenges
Friday, October 21, 2011: 3:00 PM
Room: 156ABC
Background: Despite high coverage with pertussis childhood vaccines there was a resurgence of pertussis cases in 2010, particularly in children aged 7-10 years, before the Tdap booster. Acellular pertussis vaccines have been used for all five doses since 1997, and the first birth cohorts to receive all acellular pertussis vaccine are now 7-10 years old. Waning immunity following completion of the acellular pertussis vaccine series is not well described. We calculated pertussis incidence rates among children completing the 5-dose DTaP series in the five years after receipt of the fifth dose.

Methods: These cohort analyses included children born between 1998-2003 who had five doses of DTaP recorded in the Minnesota Immunization Information Connection (MIIC), with the 5th dose received between the ages of 4 and 6 years. Immunization records were merged with Minnesota statewide pertussis surveillance data from January 1, 2004 to November 1, 2010 to identify those cohort members who developed pertussis consistent with the CSTE case definition. Incidence rates were calculated for each of the five years following completion of the 5th DTaP dose; individual level person-time was censored at age 10 or on November 1, 2010, whichever occurred first.   

Results: A total of 199,643 children were identified in our cohort; 14%, 70%, and 15% received the 5th DTaP dose at age 4, 5, and 6 years, respectively. In the 5 years of follow-up beginning at the time of receipt of their 5th DTaP dose, 358 cases of pertussis developed in this cohort. The incidence rates of pertussis in these 1-5 years of follow up were 22.5 (16.7-29.9), 29.1 (22.3-37.3), 42.4 (33.8-52.4), 54.4 (43.5-67.2), and 78.2 (63.2-95.7) per 100,000, respectively. Analyses to calculate adjusted relative rates are ongoing.

Conclusion: Incidence rates of pertussis increase in magnitude over the five years following completion of the five-dose DTaP series, suggesting waning immunity 3-5 years after the completion of the DTaP series. An evaluation of age at receipt of 5th DTaP dose as well as other factors such as differences in vaccine antigen content will inform our understanding of waning immunity prior to Tdap vaccination.


Subject Category: I. Adult and Pediatric Vaccines

Sara Tartof, PhD, MPH1, Melissa Lewis, MPH2, Cynthia Kenyon, MPH3, Karen White, MPH3, Elizabeth Zell, MStat2, Thomas Clark, MD, MPH1 and Tami Skoff, MS1, (1)Meningitis and Vaccine Preventable Diseases Branch, Centers for Disease Control and Prevention, Atlanta, GA, (2)Biostatistics, Centers for Disease Control and Prevention, Atlanta, GA, (3)Immunizations, Tuberculosis and International Health Section, Minnesota Department of Health, St. Paul, MN

Disclosures:

S. Tartof, None

M. Lewis, None

C. Kenyon, None

K. White, None

E. Zell, None

T. Clark, None

T. Skoff, None

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