Epidemic pertussis and acellular pertussis vaccine failure in the 21st century.

In this issue of Pediatrics Acosta et al present a tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis, adsorbed (Tdap) vaccine effectiveness study in adolescents in Washington State during the first 6 months of 2012. Their findings support the previous Tdap effectiveness data from Wisconsin. The duration of Tdap effectiveness is disappointing, particularly because case-control studies tend to inflate efficacy.