Bordetella Pertussis infections in vaccinated and unvaccinated adolescents and adults, as assessed in a national prospective randomized Acellular Pertussis Vaccine Trial (APERT).
BACKGROUND
Acellular pertussis (aP) booster immunizations have been recommended for adolescents and older persons to enhance long-term protection and to possibly reduce community transmission of infections.


METHODS
This was a multicenter, randomized, double-blind vaccine trial in which one-half of the subjects received aP vaccine and one-half received hepatitis A vaccine (control subjects). All subjects were observed for almost 2 years for cough illnesses, and all underwent microbiologic and serologic studies for detection of pertussis infection. Immunoglobulin G (IgG) and immunoglobulin A (IgA) antibodies to pertussis toxin, filamentous hemagglutinin, pertactin, and fimbriae 2/3 were measured by enzyme-linked immunosorbent assay in serum samples obtained 1 and 12 months after immunization. Infection rates were determined with a variety of serologic criteria for control and vaccinated subjects. The incidence of prolonged cough illness was ascertained for subjects with and subjects without serologic evidence of infection.


RESULTS
Infection rates among control subjects are particularly representative of those in nonimmunized adults. Among control subjects, 0.4%-2.7% had increases in pertussis antibody of various types and degrees over 1 year, and 20%-46% had prolonged cough illnesses during this interval. Pertussis toxin antibody had the greatest specificity for detecting increases in antibody levels. Asymptomatic infections were approximately 5 times more common than clinical illnesses that met a strict clinical and microbiologic case definition. Relative to control subjects, aP-immunized subjects may have fewer increases in the antibody level (i.e., infections), especially for antibodies to fimbriae 2/3 (an antigen not in the vaccine).


CONCLUSIONS
Pertussis infections in older persons are largely asymptomatic. aP boosters confer protection for adolescents and adults against symptomatic pertussis and likely confer protection against mild and asymptomatic infections, and use of boosters may reduce transmission to others, especially infants.
Ward
Joel I
JI
University of California-Los Angeles (UCLA) Center for Vaccine Research, Los Angeles Biomedical Research Institute, Harbor-UCLA Medical Center, David Geffen School of Medicine UCLA, Torrance, California 90502-2502, USA. joelward@ucla.edu
Cherry
James D
JD
Chang
Swei-Ju
SJ
Partridge
Susan
S
Keitel
Wendy
W
Edwards
Kathryn
K
Lee
Martin
M
Treanor
John
J
Greenberg
David P
DP
Barenkamp
Stephen
S
Bernstein
David I
DI
Edelman
Robert
R
D000293:Adolescent; D000328:Adult; D000368:Aged; D001886:Bordetella pertussis; D004311:Double-Blind Method; D006801:Humans; D007117:Immunization, Secondary; D008875:Middle Aged; D010567:Pertussis Vaccine / Q000008:administration & dosage*; D011446:Prospective Studies; D014611:Vaccination; D022282:Vaccines, Acellular; D014917:Whooping Cough / Q000517:prevention & control*
D010567:Pertussis Vaccine; D022282:Vaccines, Acellular