Tdap Vaccine Effectiveness and Duration of Protection Among Adolescents - California, 2010 Open Access

Okomo-Adhiambo, Margaret Atito (2015)

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Pertussis (whooping cough) is a highly contagious respiratory infection caused by Bordetella pertussis. In 2010, California experienced its largest pertussis epidemic in over 60 years. Despite high coverage with the 5-dose childhood diphtheria, tetanus, and whole cell or acellular pertussis vaccine series (DTP/DTaP) and a recommended tetanus-diphtheria-acellular pertussis (Tdap) booster at age 11-12 years, there were a significant number of cases among adolescents aged 11-18 years. Following this outbreak, an age-matched case-control study was conducted in 9 California counties by the Centers for Disease Control and Prevention (CDC) and the California State Department of Health (CSDH), to evaluate Tdap vaccine effectiveness (VE) and duration of protection among adolescents. Enrolled cases (n=349) were suspected, probable, and confirmed pertussis cases among adolescents aged 11 to 18 years from January through December 2010, identified through 2010 state surveillance data. Three age-matched controls per case (n=963) were selected from the same provider offices reporting the cases. Conditional logistic regression was used to calculate odds ratios (ORs) for the association between pertussis and Tdap receipt; vaccine effectiveness was estimated as (1-OR) x100%. ORs were also calculated for association between pertussis and time since Tdap receipt (<12 months, 12-23 months, 24-35 months, and ≥36 months), the association between pertussis and Tdap brand, and type of childhood pertussis series (whole cell and acellular pertussis vaccines). Among cases and controls, 183 (57.9%) and 321 (38.4%) had not received the Tdap booster, respectively. Adolescents with pertussis, compared with controls, were less likely to have received the Tdap booster (VE, 60.2%; 95% CI, 45.2%-71.2%; p<0.0001), and were also less likely to have received Tdap within the previous 12 months (VE, 73.2%; 95% CI, 57.7%-83.1%; p<0.0001). As time since Tdap vaccination increased, VE progressively declined, consistent with waning immunity from the Tdap booster.

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Appendix A: California Tdap VE Assessment Data Collection Tool...20

Appendix B: Literature Review...21

Appendix C: SAS Coding for Analysis...32

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