Pertussis in the Era of New Strains of Bordetella pertussis.

Despite implementation of a successful vaccination program, pertussis remains a significant health problem. Although the incidence of pertussis in the United States is reduced by approximately 80% compared with incidence before the introduction of vaccination in the 1940s, deaths still occur and the unrecognized disease burden remains high, with 1 million Bordetella pertussis infections annually in the United States estimated by serologic surveys. Reasons for the resurgence and current prevalence of pertussis may be multifactorial and include waning vaccine-induced protection as well as lower vaccine effectiveness, failure to vaccinate, and changes in the organism itself.