Journal Article

Pre- and Post-Conjugate Vaccine Epidemiology of Pneumococcal Serotype 6C Invasive Disease and Carriage within Navajo and White Mountain Apache Communities

Eugene V. Millar, Fabiana C. Pimenta, Alexis Roundtree, Delois Jackson, Maria da Gloria Carvalho, Mindy J. Perilla, Raymond Reid, Mathuram Santosham, Cynthia G. Whitney, Bernard W. Beall and Katherine L. O'Brien

in Clinical Infectious Diseases

Published on behalf of Infectious Diseases Society of America

Volume 51, issue 11, pages 1258-1265
Published in print December 2010 | ISSN: 1058-4838
Published online December 2010 | e-ISSN: 1537-6591 | DOI: https://dx.doi.org/10.1086/657070
Pre- and Post-Conjugate Vaccine Epidemiology of Pneumococcal Serotype 6C Invasive Disease and Carriage within Navajo and White Mountain Apache Communities

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Background. A second-generation 13-valent pneumococcal conjugate vaccine, PCV13, was recently licensed. Although PCV13 includes serotype 6A, the usefulness of that antigen may be limited by the emergence of a new serotype, 6C, which was identified among isolates initially characterized (Quellung reaction) as serotype 6A. The epidemiology of serotype 6C prior to and after 7-valent PCV (PCV7) introduction is incompletely understood.

Methods. We analyzed conventionally serotyped 6A (CS6A) pneumococci from invasive disease case patients of all ages and carriage isolates from children and adults obtained in population-based studies among Navajo and White Mountain Apache communities during 1994–2009. Samples were tested by triplex polymerase chain reaction to resolve serotypes 6C and 6A.

Results. A total of 74 invasive CS6A episodes occurred. All were retyped by polymerase chain reaction; 40 (54.1%) were serotype 6C. The mean annual incidence of serotype 6C invasive disease was 0.3 (95% confidence interval, 0.03–0.9), 0.7 (95% confidence interval, 0.2–1.3), and 1.5 (95% confidence interval, 1.0–2.1) cases per 100,000 population in the years prior to the PCV7 efficacy trial, during the time the PCV7 trial was conducted, and following PCV7 introduction and routine use, respectively (P = .01). In the routine vaccination era, 76% of invasive CS6As were serotype 6C; nearly all cases occurred in adults. The proportion of serotype 6C among CS6A carriage isolates increased from 42% to 61% to 94% in the prevaccine, early vaccine, and routine vaccination eras, respectively.

Conclusion. In the PCV7 routine use era, virtually all serogroup 6 invasive pneumococcal disease and carriage strains among Navajo and White Mountain Apache communities are 6C. Monitoring and evaluation of this and other emerging serotypes among invasive disease and carriage isolates is warranted.

Journal Article.  3968 words.  Illustrated.

Subjects: Infectious Diseases ; Immunology ; Public Health and Epidemiology ; Microbiology

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