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Several decades ago, acellular pertussis vaccines replaced whole-cell pertussis vaccines. In 2005, two vaccines containing tetanus toxoid, reduced diphtheria toxoid and reduced acellular pertussis (Tdap), were licensed for use. However, recent outbreaks and rising incidence of pertussis have raised concerns about the effectiveness of acellular pertussis vaccines. In this case-control study, investigators determined whether Tdap vaccination prevented pertussis among Kaiser Permanente members (age, ≥11 years).
From 2006 through 2011, nearly 700 polymerase chain reaction (PCR)-confirmed cases of pertussis were identified. Tdap vaccine status of confirmed cases was compared with 10,000 PCR-negative controls and 22,000 matched controls. Tdap vacc…