Where Has All the Pertussis Gone? Pertussis Trends from 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

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

Tdap Booster Vaccine Two tetanus toxoid, reduced diptheria toxoid and acellular pertussis (Tdap) vaccines licensed in 2005 ACIP Recommendations –Adolescents years; preferred age –Adults years

Tdap Coverage Among Adolescents Aged Years, National Immunization Survey – Teen, Sources: CDC. Vaccination Coverage Among Adolescents Aged Years – United States, MMWR 2008;57(40) CDC. Vaccination Coverage Among Adolescents Aged Years– United States, MMWR 2007;56(34)

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

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

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

Results

Reported Pertussis Cases, by Age Group, * *preliminary 2008 data

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

Incidence of Reported Pertussis, by Age Group, * *preliminary 2008 data

Potential Early Impact of Tdap

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

Potential Direct Effects of Tdap

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

Incidence of Reported Pertussis Among Adolescents years, * *preliminary 2008 data

Incidence of Reported Pertussis Among Adolescents years, * *preliminary 2008 data

Potential Direct Effects of Tdap: Rate ratios of pertussis incidence among adolescents years,

Slope = +0.23, p<.0001

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

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

Incidence of Reported Pertussis Among Adolescents years, 39 States †, * 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

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

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

Potential Indirect Effects of Tdap

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

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

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

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

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

Thank you

Incidence of Reported Pertussis, by Age Group, * *preliminary 2008 data

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

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