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A possible cause of recent pertussis outbreaks in the U.S. is reduced efficacy of acellular pertussis (aP) vaccines compared with whole-cell (wP) vaccines. aP vaccines were introduced in the primary vaccine series in 1997 and as a booster for adolescents in 2006. wP vaccines are no longer used, and children born after 2001 have only received aP vaccines for pertussis protection.
This retrospective study reviewed more than 260,000 patients born between 1990 and 2001 who had received wP, aP, or a combination of the two vaccine types. There were 904 cases of pertussis in patients aged 8 to 20 years. Patients who only received aP vaccines had significantly increased risk for pertussis compared with those who had received at least one wP vaccine …