Wednesday, March 19, 2008

Improving Haemophilus influenzae Serotype Reporting

Kristin H. Brown, National Center for Immunization and Respiratory Diseases/DBD/MVPD, Centers for Disease Control and Prevention, 1600 Clifton Road NE, MS C-25, Atlanta, GA, USA

Learning Objectives for this Presentation:
By the end of the presentation participants will be able to evaluate serotype completeness in surveillance data and identify potentials error sources.

National surveillance for invasive Haemophilus influenzae (Hi) disease is carried out through state-based passive reporting to the National Notifiable Diseases Surveillance System (NNDSS). Invasive serotype b (Hib) disease in children <5 years of age is notifiable in all states. Provisional 2006 data (MMWR week 52) included 300 cases of invasive Hi in children <5 years of age, with 8 identified as Hib. Serotype was missing or unknown for 210(70%) cases.

The goal of this project was to improve serotype completeness in NNDSS to ensure national surveillance can detect changes in Hib epidemiology, thereby strengthening vaccine program evaluation.

Twenty-two states with missing serotype data were contacted, beginning with states with consistently incomplete data. Several states requested assistance in response to surveillance indicators reports, distributed by the NCIRD surveillance office, which included measures of Hi data completeness. States were asked to update serotype in NNDSS; NNDSS data were supplemented with data reported to the program and from Active Bacterial Core surveillance.

Final 2006 NNDSS data included 389 cases of Hi in children <5 years of age. When supplemental data was included, 33 cases of Hib disease were identified, a 32% improvement; serotype was unknown or missing for 150(38%) cases. Much of the missing data was associated with previously unidentified systematic errors in state or national electronic data transmission and management. One error caused 20% of serotype data to be excluded from the NNDSS dataset: the error was corrected and data included in final 2006 MMWR numbers.

Continuous monitoring of NNDSS surveillance data quality and feedback to states is necessary for data to be used for immunization program evaluation and to detect changes in Hib epidemiology, particularly as Hib incidence declines.