1. Where Has All the Pertussis Gone? Pertussis Trends from 1990-2008 and the Potential Early Impact of Tdap Vaccination National Immunization Conference Dallas, TX April 1, 2009 T.H. Skoff 1, K. Brown 1, A. Cohn 1, J. Liang 1, T. Clark 1, N. Messonnier 1, S.W. Martin 1. CDC, Atlanta, GA 1

2. Pertussis Characterized by paroxysmal cough, posttussive vomiting and inspiratory whoop –Dependent on history of vaccination or previous exposure Vaccine-preventable; however, remains substantial public health problem in the U.S. –Highest morbidity and mortality among infants –Increasing in adolescents and adults –Older age groups as reservoir for transmission to infants

3. Tdap Booster Vaccine Two tetanus toxoid, reduced diptheria toxoid and acellular pertussis (Tdap) vaccines licensed in 2005 ACIP Recommendations –Adolescents 11-18 years; 11-12 preferred age –Adults 19-64 years

4. Tdap Coverage Among Adolescents Aged 13-17 Years, National Immunization Survey – Teen, 2006-2007 Sources: CDC. Vaccination Coverage Among Adolescents Aged 13-17 Years – United States, 2007. MMWR 2008;57(40)1100-1103 CDC. Vaccination Coverage Among Adolescents Aged 13-17 Years– United States, 2006. MMWR 2007;56(34) 885-888.

5. Objectives Describe trends in reported pertussis in the U.S. between 1990–2008 Explore the early potential direct and indirect impact of Tdap vaccination

6. Methods Nationally Notifiable Diseases Surveillance System (NNDSS); 1990–2007, preliminary 2008 Incidence Rates –Numerators: cases reported through NNDSS –Denominators: National Center for Health Statistics postcensal population estimates

7. CSTE Case Definition Clinical case definition: Cough >2 weeks AND paroxysms, inspiratory whoop, or posttussive vomiting *Data collection for PCR and epi-link began in 1995 ProbableConfirmed -Meets clinical case definition - Culture positive + cough any duration - PCR* + clinical case definition - Epi link* + clinical case definition

8. Results

9. Reported Pertussis Cases, by Age Group, 1990-2008* *preliminary 2008 data

10. Incidence of Reported Pertussis, 1990-2008* % Change (between 2005 and 2008): -61.7% (-62.6%,-60.8%) Tdap *preliminary 2008 data

11. Incidence of Reported Pertussis, by Age Group, 1990-2008* *preliminary 2008 data

12. Potential Early Impact of Tdap

13. Impact of Tdap Direct Effects - Protection for vaccinated individuals; “vaccine effectiveness” Indirect Effects – Impact on infant disease; “herd immunity”

14. Potential Direct Effects of Tdap

15. Methods for Monitoring the Direct Effects of Tdap Rate Ratio = Incidence among cases 11-18 years Incidence in all other age groups Segmented regression analysis used to evaluate Tdap impact over time –Pre-Tdap: 1990-2004 –Post-Tdap: 2005-2008

16. Incidence of Reported Pertussis Among Adolescents 11-18 years, 1990-2008* *preliminary 2008 data

17. Incidence of Reported Pertussis Among Adolescents 11-18 years, 1990-2008* *preliminary 2008 data

18. Potential Direct Effects of Tdap: Rate ratios of pertussis incidence among adolescents 11-18 years, 1990-2004

19. Slope = +0.23, p<.0001

20. Potential Direct Effects of Tdap: Rate ratios of pertussis incidence among adolescents 11-18 years, 2004-2008* Slope = -0.55, p<.0001 Slope = +0.23, p<.0001 *preliminary 2008 data

21. Incidence of Reported Pertussis Among Adolescents 11-18 years, 39 States †, 1990-2008* †Excludes data from states with annual incidence >20/100,000 in 2004 or 2005 (n=11) *Preliminary 2008 data

22. Incidence of Reported Pertussis Among Adolescents 11-18 years, 39 States †, 1990-2008* Avg. Rate Difference (’04-’05): -10.5/100,000 †Excludes data from states with annual incidence >20/100,000 in 2004 or 2005 (n=11) *Preliminary 2008 data

23. Potential Direct Effects of Tdap: Rate ratios of pertussis incidence among adolescents 11-18 years, 39 States †, 2004-2008* †Excludes data from states with annual incidence >20/100,000 in 2004 or 2005 (n=11) *preliminary 2008 data

24. Potential Direct Effects of Tdap: Rate ratios of pertussis incidence among adolescents 11-18 years, 39 States †, 2004-2008* Slope= - 0.32, p=0.002 Slope= + 0.18, p<.0001 †Excludes data from states with annual incidence >20/100,000 in 2004 or 2005 (n=11) *preliminary 2008 data

25. Potential Indirect Effects of Tdap

26. Potential Indirect Effects of Tdap? Incidence of Reported Pertussis Among Infants <1 Year, 1990-2008* *preliminary 2008 data

27. Potential Indirect Effects of Tdap? Average Incidence of Reported Pertussis Among Infants <1 Year 1990-2003 (pre-peak) 2006-2008 (post-peak) Average Incidence (infants <1 year ) 52.2/100,00045.3/100,000 Rate Difference: -6.8/100,000 Comparison of Means: p=0.3240

28. Summary Significant changes in rates of disease among adolescents 11-18 years compared to other age groups –Early direct impact of Tdap? No significant changes observed among infants <1 year, but still early

29. Is Tdap responsible for all of the decline? Likely some early benefits of Tdap –However, some decline observed prior to introduction of Tdap Multiple factors may contribute to decreasing rates among adolescents –Population immunity (natural boosting) –Changes in testing and reporting patterns –Cyclical patterns of disease

30. Conclusions Early surveillance data promising –Suggests some benefits of Tdap Continued monitoring of pertussis trends important to further evaluate impact of Tdap

31. Thank you

32. Incidence of Reported Pertussis, by Age Group, 1990-2008* *preliminary 2008 data

33. Percent Change in the Incidence of Reported Pertussis, By State, 2005-2008 *preliminary 2008 data Range: -1.7% to 99.8% Range: +9.4% to +80.9%

34. Reported Pertussis Cases -- U.S., 1922-2008* DTP SOURCE: CDC, National Notifiable Diseases Surveillance System and Supplemental Pertussis Surveillance System and 1922-1949, passive reports to the Public Health Service *2008 data is provisional DTaPTdap