Amanda E. Faulkner, MPH Surveillance Coordinator 2011 National Immunization Conference March 30, 2011 Zooming in on Pertussis Epidemiology in the United States National Center for Immunization & Respiratory Diseases Meningitis and Vaccine Preventable Diseases Branch

Pertussis Background  Caused by Bordetella pertussis bacteria  Vaccine-preventable and poorly controlled  Reports peak in 3-5 year cycles but vary by geographic regions  Infants at greatest risk for severe illness

It’s Back… Pertussis in

Objectives  Describe U.S. regional pertussis trends during  Age-incidence  Infant case fatality rates  Outbreak-related cases  Discuss challenges in reporting and interpreting surveillance data  Explore ways to improve national pertussis surveillance data

Pertussis Surveillance in the U.S.  Reportable in 1922  National case-based investigations tracked 1979  National Notifiable Disease Surveillance System (NNDSS)  Reports received from all 50 states  Passive surveillance system  Data received  Core variables  Extended variables

CSTE Pertussis Case Definition  Clinical case definition:  Cough > 2 weeks AND  paroxysms, inspiratory whoop, or posttussive vomiting Case Classification ProbableConfirmed - Meets clinical case definition - Culture positive - PCR + clinical case definition - Epi link + clinical case definition

METHODS

Methods  NNDSS data:  2009 final and 2010 provisional datasets  Confirmed, probable, unknown case status Designated by state coding scheme  Cases divided into 9 MMWR geographic reporting regions

MMWR Geographic Regions I: New England II: Mid Atlantic III: E.N. Central IV: W.N. Central V: South Atlantic VI: E.S. Central VII: W.S. Central VIII: Mountain IX: Pacific

Methods  2-year cumulative incidence calculations:  Numerator: Cases reported during  Denominator: 2009 census data estimates  Incidence ranges defined by quartiles  Age groups assessed:  < 1 year  1-4 years  5-6 years  7-10 years  years  years  20+ years

Methods  Infant case fatality rates (CFRs)  Numerator: Deaths reported among cases < 1 year of age  Denominator: All cases among those < 1 year of age  Outbreak-related cases  Used NETSS Outbreak Associated variable  Proportions calculated using only cases with known outbreak status as denominator

RESULTS

U.S. Pertussis Incidence: Source : CDC National Notifiable Disease Surveillance System, 2009 final and 2010 provisional data CDC Wonder Population Estimates (Vintage 2009) *Projection is based on an estimated 30% increase between provisional and final datasets Incidence: Projected 2010 Provisional 2010

Pertussis Incidence by State, * Cumulative incidence is per 100,000 population Source : CDC National Notifiable Disease Surveillance System, 2009 final and 2010 provisional data CDC Wonder Population Estimates (Vintage 2009) Incidence*

Pertussis Incidence by MMWR Region, * Cumulative incidence is per 100,000 population Source : CDC NNDSS, 2009 final and 2010 provisional data, CDC Wonder Population Estimates (Vintage 2009) Incidence* IX: Pacific (Range: ) VIII: Mountain (Range: ) IV: W.N. Central (Range: ) VII: W.S. Central (Range: ) III: E.N. Central (Range: ) VI: E.S. Central (Range: ) V: South Atlantic (Range: ) II: Mid Atlantic (Range: ) I: New England (Range: )

Pertussis Incidence by MMWR Region, * * Cumulative incidence is per 100,000 population Source : CDC NNDSS, 2003 and 2004 final data, CDC Wonder Population Estimates (Vintage 2003) Incidence IX: Pacific VIII: Mountain IV: W.N. Central VII: W.S. Central III: E.N. Central VI: E.S. Central V: South Atlantic II: Mid Atlantic I: New England

Pertussis Incidence by MMWR Region, U.S. Incidence: 12.43

Reported Pertussis Cases by Regional Population,

Pertussis Incidence by Age and Region,

Infant Pertussis Case Fatality Rates by Region, * Denominator for CFR calculations was all reported infant cases.

Proportion of Pertussis Cases Associated with an Outbreak, by Region, *Only includes cases with known outbreak status; 40% of overall reported cases had unknown status.

Summary  Overall pertussis incidence varied significantly by state and region in  Trends in age-specific incidence are similar across regions  Greatest incidence among < 1 year olds  Unexpected regional differences were noted  More populous regions do not necessarily report higher proportions of cases  Infant case fatality rates do not correspond with incidence among infants  Regional proportions of outbreak-related cases vary widely

DISCUSSION

What Do These Findings Mean?  Real differences by region?  Surveillance artifacts?  Surveillance capacity  Testing practices  Provider recognition of pertussis

Factors Impacting NNDSS Pertussis Data Quality  Lack of adherence to CSTE case definition  Incomplete case data  Differences in variable interpretation

Suggestions for Improved Reporting  Appropriate case reporting based on standard CSTE case definition  Complete case data  Standardization of variable interpretation

Conclusions  Differences in regional pertussis epidemiology exist, but interpretation is difficult  Efforts should focus on improving completeness of data and adhering to the CSTE case definition  Better understanding of regional trends in pertussis is key for programmatic and policy decision-making

Acknowledgements Tami Skoff Grace Ejigiri Stacey Martin Tom Clark Nancy Messonnier

For more information please contact Centers for Disease Control and Prevention 1600 Clifton Road NE, Atlanta, GA Telephone, CDC-INFO ( )/TTY: Web: The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention. Thank you! National Center for Immunization & Respiratory Diseases Meningitis and Vaccine Preventable Diseases Branch