643. Using an Immunization Information System (IIS) to Estimate the Effectiveness of Tdap in Preventing Pertussis During a Large Outbreak, Wisconsin, July 2011-December 2012
Session: Oral Abstract Session: Vaccines for all Ages
Friday, October 4, 2013: 9:45 AM
Room: The Moscone Center: 200-212
Background: During 2011-2012, a statewide outbreak of pertussis occurred in Wisconsin (WI).  Pertussis incidence was highest among infants and persons aged 10-14 years. Required receipt of tetanus-diphtheria-acellular pertussis vaccine (Tdap) was phased in during 2008-2010 for all WI students in grades 6-12. We estimated Tdap effectiveness in preventing pertussis among adolescent age cohorts never immunized with whole cell pertussis vaccine.

Methods: We defined the surveillance population (SP) as WI residents born during 1998-2001 with client records in the population-based WI Immunization Registry (WIR). A pertussis case was defined as an acute cough illness with onset during 7/1/2011-12/31/2012 (outbreak interval) in a SP member with laboratory-confirmed Bordetella pertussis infection meeting the CSTE definition of “confirmed”. Pertussis cases were matched to WIR client records by name and birth date. Tdap brand and date received were obtained from the WIR. The population unexposed to Tdap was estimated based on census data assuming all Tdap doses received were documented in the WIR.  Rates of pertussis among individuals exposed and unexposed to Tdap were calculated by brand and timing of receipt.  Age-adjusted relative risks and vaccine effectiveness (VE) estimates were calculated using Poisson regression.

Results: Of 1,464 reported cases among the 306,142-member SP, 1450 (99%) were successfully matched to WIR client records.  Overall Tdap VE was 68.6% (95% CI: 64.8%-71.9%). VE decreased from 87.3% (84.8%-89.5%) among those vaccinated during the outbreak interval to 44.1% (34.5%-52.2%) among those vaccinated during 1/1/2010-6/30/2011 to 11.4% (-8.4%-27.6%) among those vaccinated during 7/1/2008-12/31/2009. VE was greater and longer-sustained during these three time periods among Boostrix recipients (92.6%, 60.0%, 31.4%) than among Adacel recipients (84.1%, 23.4%, -3.3%).

Conclusion: Tdap is effective in preventing laboratory-confirmed pertussis in the short-term, but immunity wanes quickly. Boostrix appears to induce longer-lasting immunity than Adacel, but these findings need to be confirmed in additional studies. This study demonstrates the usefulness of an IIS to examine vaccine effectiveness within a population.

Ruth Koepke, MPH1,2, Jens Eickhoff, PhD2, Roman Aydiko Ayele, MPH1,2, Ashley Richardson-Haleem, MPH1,2, Stephanie Schauer, PhD1, Thomas Maerz1, Daniel Hopfensperger, BS1, James Conway, MD FAAP2 and Jeffrey Davis, MD1, (1)Wisconsin Department of Health Services, Division of Public Health, Madison, WI, (2)University of Wisconsin School of Medicine and Public Health, Madison, WI

Disclosures:

R. Koepke, Sanofi Pasteur: Research Contractor, Salary

J. Eickhoff, None

R. Aydiko Ayele, Sanofi Pasteur: Research Contractor, Salary

A. Richardson-Haleem, Sanofi Pasteur: Research Contractor, Salary

S. Schauer, None

T. Maerz, None

D. Hopfensperger, None

J. Conway, Sanofi Pasteur: Grant Investigator and Scientific Advisor, Consulting fee, Research grant and Research support

J. Davis, Sanofi Pasteur: Grant Investigator, Research grant

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