title: Efficacy of an acellular pertussis vaccine among adolescents and adults.
abstract: BACKGROUND
  Pertussis immunization of adults may be necessary to improve the control of a rising burden of disease and infection. This trial of an acellular pertussis vaccine among adolescents and adults evaluated the incidence of pertussis, vaccine safety, immunogenicity, and protective efficacy.
  
  
  METHODS
  Bordetella pertussis infections and illnesses were prospectively assessed in 2781 healthy subjects between the ages of 15 and 65 years who were enrolled in a national multicenter, randomized, double-blind trial of an acellular pertussis vaccine. Subjects received either a dose of a tricomponent acellular pertussis vaccine or a hepatitis A vaccine (control) and were monitored for 2.5 years for illnesses with cough that lasted for more than 5 days. Each illness was evaluated with use of a nasopharyngeal aspirate for culture and polymerase-chain-reaction assay, and serum samples from patients in both acute and convalescent stages of illness were analyzed for changes in antibodies to nine B. pertussis antigens.
  
  
  RESULTS
  Of the 2781 subjects, 1391 received the acellular pertussis vaccine and 1390 received the control vaccine. The groups had similar ages and demographic characteristics, and the median duration of follow-up was 22 months. The acellular pertussis vaccine was safe and immunogenic. There were 2672 prolonged illnesses with cough, but the incidence of this nonspecific outcome did not vary between the groups, even when stratified according to age, season, and duration of cough. On the basis of the primary pertussis case definition, vaccine protection was 92 percent (95 percent confidence interval, 32 to 99 percent). Among unimmunized controls with illness, 0.7 percent to 5.7 percent had B. pertussis infection, and the percentage increased with the duration of cough. On the basis of other case definitions, the incidence of pertussis in the controls ranged from 370 to 450 cases per 100,000 person-years.
  
  
  CONCLUSIONS
  The acellular pertussis vaccine was protective among adolescents and adults, and its routine use might reduce the overall disease burden and transmission to children.
authors.affiliation: UCLA Center for Vaccine Research, Research and Education Institute, Harbor-UCLA Medical Center, David Geffen School of Medicine, UCLA, Torrance, Calif 90502, USA.
authors.forename: Joel I
authors.initials: JI
authors.lastname: Ward
authors.forename: James D
authors.initials: JD
authors.lastname: Cherry
authors.forename: Swei-Ju
authors.initials: SJ
authors.lastname: Chang
authors.forename: Susan
authors.initials: S
authors.lastname: Partridge
authors.forename: Hang
authors.initials: H
authors.lastname: Lee
authors.forename: John
authors.initials: J
authors.lastname: Treanor
authors.forename: David P
authors.initials: DP
authors.lastname: Greenberg
authors.forename: Wendy
authors.initials: W
authors.lastname: Keitel
authors.forename: Stephen
authors.initials: S
authors.lastname: Barenkamp
authors.forename: David I
authors.initials: DI
authors.lastname: Bernstein
authors.forename: Robert
authors.initials: R
authors.lastname: Edelman
authors.forename: Kathryn
authors.initials: K
authors.lastname: Edwards
mesh_terms: D000293:Adolescent; D000328:Adult; D001886:Bordetella pertussis / Q000302:isolation & purification; D004311:Double-Blind Method; D005260:Female; D022362:Hepatitis A Vaccines; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010567:Pertussis Vaccine / Q000009:adverse effects / Q000276:immunology; D016896:Treatment Outcome; D014917:Whooping Cough / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology / Q000517:prevention & control*
chemical_list: D022362:Hepatitis A Vaccines; D010567:Pertussis Vaccine