Objectives: To determine the prevalence of Bordetella pertussis infection among adults who have prolonged cough for 2 weeks or longer and to estimate the incidence of B pertussis infection in adults in a defined urban population.
Design: A prospective clinical study.
Setting: Kaiser Permanente, San Francisco (Calif) Medical Center.
Participants: One hundred fifty-three referred and participating health plan members 18 years old or older with the complaint of cough persisting for 2 weeks or longer and 154 health plan members 18 years old or older with no cough for the past 3 months (controls) were enrolled. Medical records for an additional 100 patients randomly sampled from 676 patients 18 years old or older with an ambulatory diagnosis of cough (60 with prolonged cough) were also reviewed.
Main outcome measures: Prevalence of adult pertussis as determined by enzyme-linked immunosorbent assay IgG antibody levels to pertussis toxin in individuals with prolonged cough for 2 weeks or longer and the incidence of adult pertussis in San Francisco Kaiser health plan members.
Results: The prevalence of adult pertussis was 12.4% of the participating referrals. The incidence of adult pertussis was estimated to be 176 cases per 100 000 person-years (95% confidence interval, 97 to 255 cases).
Conclusions: Adult pertussis is a significantly greater public health threat than previously suspected. Booster doses of acellular pertussis vaccine after 7 years of age may be an effective approach to minimize transmission and infection.