METHODS: Pertussis cases reported through NNDSS during 2010 through 2014 were included in this analysis. Reported deaths among pertussis cases were analyzed by state of residence, age at cough onset, and clinical presentation (cough, cough duration, paroxysms, whoop, post-tussive vomiting, hospitalization status). Deaths reported among patients ≥ 1 year of age were further assessed by obtaining medical charts, death certificates and investigation notes, when available, to identify clinically relevant data not routinely reported through NNDSS. We compared National Center for Health Statistics (NCHS) death records with a pertussis ICD-9/10 codes against NNDDS, and surveyed state health departments to better define current death reporting practices for pertussis cases.
RESULTS: During the study period 86 deaths were reported by 30 states through NNDSS. Annual overall case fatality among pertussis cases ranged from 0.04% to 0.1%. The majority of deaths (73/86; 85%) occurred among infants aged < 1 year. Eight states reported 13 deaths among pertussis patients ≥ 1 year of age. Clinical symptoms reported through NNDSS was complete for 53% of reported deaths; 76% had known vaccination status. NNDSS captured an annual average of 2 additional pertussis deaths (range: 0-6) as compared to NCHS. States described variations in death reporting; while some respondents only report deaths that have been validated through death certificate review, others indicated that deaths in laboratory- or clinically-diagnosed pertussis cases were reportable in their jurisdictions.
CONCLUSIONS: Pertussis death reporting and validation practices are not standardized nationally, which may impair our understanding of pertussis mortality and limit our ability to assess for contributing risk factors. Additionally, clinical information received through NNDSS is not available for all reported pertussis deaths. The Council for State and Territorial Epidemiologists has called for harmonization of data elements for notifiable conditions, as well as standardization of the death validation processes. Accordingly, CDC and state partners should work together to establish standardized death validation and reporting procedures for pertussis cases.