Abstract: The Use of Immunization Information Systems (IISs) in Vaccine Effectiveness Studies (43rd National Immunization Conference (NIC))

42 The Use of Immunization Information Systems (IISs) in Vaccine Effectiveness Studies

Tuesday, March 31, 2009: 2:25 PM
Lone Star Ballroom C2
Julie A. Boom
Manish Patel
Umesh D. Parashar
Marcia A. Rench
Carol J. Baker
Jacqueline E. Tate

Recently, many new vaccines have been added to the childhood immunization schedule. Post-licensure effectiveness studies of these vaccines have typically relied on data collected through active surveillance involving the enrollment of comparison groups. Obtaining immunization data for enrolled patients is time-consuming and often requires extensive follow-up. IISs could represent easily accessible sources of immunization data and be used as a source of control patients, thus eliminating the need to enroll a comparison group.

1. To validate immunization information obtained from an IIS against provider records;
2. To assess the utility of an IIS in evaluating vaccine effectiveness.

A convenience sample of pediatric emergency room patients was enrolled in a study assessing the effectiveness of pentavalent rotavirus vaccine (RV5). When available, a copy of each child's immunization record was obtained from the parent/guardian. Permission was obtained to search the Houston-Harris County Immunization Registry (HHCIR) and contact the child's immunization provider(s). Vaccine effectiveness (VE) was calculated using 2 concurrently enrolled control groups (rotavirus-negative acute gastroenteritis (AGE) and acute respiratory infection (ARI) patients) and compared with VE using controls randomly selected from HHCIR.

45% (n=285) of enrolled patients had immunizations in HHCIR. Provider records were obtained for 93% (n=266) of these children. HHCIR data were the same as the provider record for 71% (n=189) of patients. The HHCIR record contained additional immunization data for 11% (n=30) and was less complete for 18% (n=47) of patients with both records.
VE for a full RV5 series was 89%, 85%, and 82% using rotavirus-negative AGE, ARI, and HHCIR-selected control patients, respectively.

Although immunization data for only 45% of patients were available from HHCIR, VE calculated using IIS data was similar to estimates using the other control groups. IISs could represent a valuable source of data for VE evaluations.