[3380.7] The Effect of the 2011-2012 Pertussis Epidemic on Infant DTaP Vaccination in Washington State

Elizabeth R. Wolf, Douglas Opel, M. Patricia deHart, Jodi Warren, Ali Rowhani-Rahbar. Seattle Children's Research Institute, Seattle, WA; Department of Pediatrics, University of Washington, Seattle, WA; Washington State Department of Health, Olympia, WA; Washington State Immunization Information System, Seattle, WA; Department of Epidemiology, University of Washington, Seattle, WA.

BACKGROUND: Washington State experienced a pertussis epidemic from October 2011 to December 2012. There was considerable variation in incidence by county; rates were highest amongst infants.
OBJECTIVE: To determine the effect of the pertussis epidemic on diphtheria-tetanus toxoid-acellular pertussis (DTaP) vaccination rates in infants in Washington State and whether incidence in county of residence modified this effect.
DESIGN/METHODS: We conducted an ecologic before-after study in which we compared the proportion of infants up to date (UTD) with DTaP at time points before (September 30, 2011) and during (September 30, 2012) the epidemic. Children aged 3-8 months with at least one record in the Washington State Immunization Information System and documented county of residence were included. UTD status was determined by ≥1, ≥2, or ≥3 DTaP doses at ages 3, 5, and 7 months, respectively. We used generalized linear models with extension to the binomial family and clustered robust standard errors to examine differences in proportion of infants UTD with DTaP between pre-epidemic and epidemic points. To evaluate for effect modification, we categorized counties by pertussis incidence tercile and tested the interaction term for significance.
RESULTS: There were 39,500 and 40,811 children included at the pre-epidemic and epidemic time points, respectively. We found no significant difference in infant UTD status with DTaP between pre-epidemic and epidemic time points on the state level (absolute difference: 2.1%; 95% CI: -1.6, 5.9). There was no significant modification of this association by pertussis incidence in county of residence, although there was considerable variability in the absolute difference across counties (Figure 1).

Figure 1. Difference in proportion of infants up to date with DTaP comparing time points before and during pertussis epidemic.
CONCLUSIONS: The 2011-2012 pertussis epidemic did not significantly change DTaP vaccination rates among infants in Washington State.
First Author is a Fellow in Training

Session: Platform Session: General Pediatrics: Data Driven Change (10:30 AM - 12:30 PM)
Date/Time: Monday, May 5, 2014 - 12:00 PM
Room: East 12 - Vancouver Convention Centre
Course Code: 3380


Close Window