BACKGROUND:
The pertussis vaccine has been used in children for several decades with a range of success. Oregon’s immunization rates remain low, 91.3% of Oregon 2 year-olds had 3 doses of DTaP in 2002 as opposed to 94.4% throughout the United States.

OBJECTIVE:
To examine the rate of DTaP vaccination in child pertussis cases reported in Oregon during 2002 and 2003.

METHOD:
An analysis of the immunization status of 198 (93.8%) pertussis cases 2 months - 10 years of age submitted by local health departments (LHDs) during 2002 and 2003 was conducted. The LHD interviewed each case’s parent. Using the results of the case interview and data from Immunization ALERT, Oregon’s immunization registry, the number pertussis vaccine doses received, time elapsed since previous DTaP, and any reasons reported by the parent for not ensuring their child was immunized. Few cases, 13 (6.2%) were excluded due to missing dates of vaccination. Doses administered within 2 weeks of cough onset were also excluded.

RESULT:
Oregon’s pertussis cases are considerably under immunized compared to their peers. The mean age of the 198 cases was 3.1 years. The mean lag from the last valid dose of DTaP to cough onset was 24.1 months. The majority of cases were unvaccinated (38.9%) or vaccinated with 1-2 doses of pertussis vaccine (21.7%); only 39.4% had at least 3 doses of pertussis-containing vaccine. Of the parents of partially vaccinated and unvaccinated children (n=120), 44.4% reported personal choice or religious objection to vaccination, 10.3% reported vaccine safety concerns, and 3.8% refused DTaP, choosing DT instead.

CONCLUSION:
Few cases were fully immunized, indicating that the risk of disease continues and its unlikely that vaccine failure is contributing to the increase in pertussis.

LEARNING OBJECTIVES:
Describe reasons for failing to vaccinate in Oregon children who develop pertussis.