During a 2012 outbreak of pertussis in Wisconsin, inoculation of adolescents with Tdap vaccinations showed dwindling immunity with time, according to recent findings.
Although the Boostrix (GlaxoSmithKline) Tdap vaccine demonstrated greater efficacy than Adacel (Sanofi-Pasteur), these findings may not be generalizable to other adolescents who received different DTaP vaccines during childhood, the researchers wrote.
The researchers utilized data from the population-based Wisconsin Immunization Registry to track the effectiveness of Tdap by brand and year of receipt. The registry is a statewide immunization information system that chronicles and monitors immunization histories for all residents of Wisconsin.
The researchers found that, overall, Tdap efficacy after time of receipt declined as follows: 75.3% (95% CI, 55.2-86.5) for vaccines received in 2012; 68.2% (95% CI, 60.9-74.1) for vaccines received during 2011; 34.5% (95% CI, 19.9-46.4) for vaccines received in 2010; and 11.9% (95% CI, –11.1% to 30.1%) for vaccines received during 2008-2009.
According to the researchers, increased time since vaccination was associated with increased pertussis risk. Vaccination with Boostrix was associated with a 38% reduced risk for pertussis infection in comparison to vaccination with Adacel (IRR=0.62; 95% CI, 0.52-0.74).
“Our results demonstrate waning immunity following Tdap vaccination with either brand,” the researchers wrote. “Boostrix was more effective than Adacel in preventing pertussis among our cohort, but these findings may not be generalizable to adolescent cohorts that received different DTaP vaccines, and should be further examined in studies that included childhood DTaP history.”
Disclosure: Some of the researchers received funding from Sanofi-Pasteur for an unrelated study. Another researcher is the coordinating investigator of a grant from Sanofi-Pasteur and does not receive salary support, but did receive funding for travel.