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California’s 2014 pertussis epidemic came right on schedule. Outbreaks peak every 3 to 5 years in the United States, with the last epidemic in the state occurring in 2010 when 9000 cases were reported (24.6 cases per 100 000 population). Last year, from January 1 to November 26, 9935 pertussis cases were reported in California (26 cases per 100 000)—the most in nearly 70 years.
The highest incidence of pertussis was among California infants younger than 1 year, 174.6 cases per 100 000, and the rate was significantly higher among Hispanic infants. Among the infants younger than 1 year who were hospitalized for pertussis, only 24% had received any doses of diphtheria, tetanus, and acellular pertussis vaccine (DTaP). Even fewer mothers (17%) of infants younger than 4 months reported receiving tetanus, diphtheria, and acellular pertussis vaccine (Tdap) while pregnant (Winter K et al. MMWR Morb Mortal Wkly Rep. 2014;63:1129-1132).
New Normal in Pertussis Incidence. JAMA. 2015;313(6):559. doi:10.1001/jama.2015.146