139. Vaccine Effectiveness and Duration of Protection of Tetanus Toxoid, Reduced Diphtheria Toxoid and Acellular Pertussis among Adolescents, Washington State, 2012
Session: Poster Abstract Session: Adult and Pediatric Vaccines
Thursday, October 3, 2013
Room: The Moscone Center: Poster Hall C
Background: Beginning in 1997, acellular pertussis (aP) vaccines replaced whole-cell vaccines for the entire childhood vaccination series. A sixth dose of pertussis-containing vaccine, tetanus toxoid, reduced diphtheria toxoid and acellular pertussis (Tdap), was recommended in 2005 for adults and adolescents, with preferred administration at 11-12 years. In 2012, Washington State declared a pertussis epidemic with a record 4,921 cases reported. Despite high vaccine coverage with Tdap, an unexpectedly high disease incidence was observed in adolescents 13-14 years of age – the first birth cohorts to be vaccinated exclusively with aP vaccines – suggesting early waning of immunity. 

Methods: We conducted a matched case-control study in Washington State to assess Tdap vaccine effectiveness (VE) and duration of protection among adolescents 11-14 years of age. Pertussis cases reported in counties with greater than 50 cases from January 1 to June 30, 2012 were included. Cases were identified using Washington State surveillance definitions. Three controls were matched by healthcare provider and birth year to each case. Vaccination history was obtained through medical records, the state immunization registry and parent interviews. Odds ratios (ORs) comparing Tdap receipt between cases and controls were calculated using conditional logistic regression. VE was estimated as (1 - OR) × 100%.

Results: A total of 472 cases and 1362 controls were included in the analysis. Tdap vaccination status was verified in 94% of these subjects. Excluding those not verified, 77% (352/458) of cases and 88% (1119/1266) of controls received Tdap. Preliminary analysis showed an overall VE of 66% (95% confidence interval [CI]: 52-76%). VE within one year of Tdap vaccination was 75% (95% CI: 62-83%). At 2 or more years post-vaccination, VE declined to 41% (95% CI: 7-63%).  

Conclusion: This is the first study to estimate Tdap VE and duration of protection among adolescents who would have been vaccinated solely with aP vaccines. Preliminary results indicate that Tdap VE is modest and wanes substantially with time. Although current Tdap vaccines may not fully control pertussis in the United States, vaccination remains the best way to protect individuals against disease.

Anna M. Acosta, MD1, Chas Debolt, RN, MPH2, Azadeh Tasslimi, MPH2, Melissa Lewis, MPH3, Laurie Stewart, MS2, Lara K. Misegades, PhD, MS1, Nancy E. Messonnier, MD1, Thomas A. Clark, MD, MPH1, Stacey W. Martin, MS1 and Manisha Patel, MD, MSc1, (1)Meningitis and Vaccine Preventable Diseases Branch, Centers for Disease Control and Prevention, Atlanta, GA, (2)Communicable Disease Epidemiology, Washington State Department of Health, Shoreline, WA, (3)Biostatistics Office, Division of Bacterial Diseases, Centers for Disease Control and Prevention, Atlanta, GA


A. M. Acosta, None

C. Debolt, None

A. Tasslimi, None

M. Lewis, None

L. Stewart, None

L. K. Misegades, None

N. E. Messonnier, None

T. A. Clark, None

S. W. Martin, None

M. Patel, None

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