title: Impact of 13-Valent Pneumococcal Conjugate Vaccination on Streptococcus pneumoniae Carriage in Young Children in Massachusetts.
abstract: BACKGROUND
  In April 2010, a 13-valent pneumococcal conjugate vaccine (PCV13) replaced PCV7 for use in the United States. We evaluated rates of pneumococcal colonization, by serotype and antibiotic resistance, in Massachusetts communities where serial cross-sectional surveillance has been conducted for the past decade.
  
  
  METHODS
  Nasopharyngeal swabs were obtained from children 0 to <7 years of age and seen by primary care providers for well child or acute illness visits in 2001, 2004, 2007, 2009, and 2011. Pneumococcal isolates were serotyped by Quellung reaction and classified as PCV7 serotypes (4, 6B, 9V, 14, 18C, 19F, 23F), additional PCV13 serotypes (1, 3, 5, 6A, 7F, 19A), or non-PCV13 serotypes. Changes in colonization and impact of PCV13 were assessed using generalized linear mixed models, adjusting for known risk factors and accounting for clustering by community.
  
  
  RESULTS
  Introduction of PCV13 did not affect the rate of overall pneumococcal colonization (31% in 2011). Colonization with non-PCV13 serotypes increased between 2001 and 2011 for all children (odds ratio [OR] per year, 1.12; 95% confidence interval [CI], 1.10, 1.15; P < .0001). 19A remained the second most common serotype in 2011, although a decline from 2009 was observed. Penicillin (7%), erythromycin (28%), ceftriaxone (10%), and clindamycin (10%) nonsusceptibility were commonly identified, concentrated among a small number of serotypes (including 19A, 35B, 15B/C, and 15A). Among healthy children 6-23 months old, colonization with PCV13 serotypes was lower among recipients of PCV13 vaccine (adjusted OR, 0.30; 95% CI, 0.11, 0.78). This effect was not observed in 6- to 23-month-old children with a concomitant respiratory tract infection (adjusted OR 1.36; 95% CI, 0.66, 2.77) or children 2 to <7 years old (adjusted OR, 1.17; 95% CI, 0.58, 2.34).
  
  
  CONCLUSIONS
  13-Valent pneumococcal conjugate vaccine reduced the prevalence of colonization with PCV13 serotypes among children 6-23 months old, but its efficacy was not shown among older children.
authors.affiliation: Center for Child Health Care Studies, Department of Population Medicine, Harvard Pilgrim Health Care Institute and Harvard Medical School Division of Infectious Diseases and Department of Laboratory Medicine, Boston Children's Hospital.
authors.forename: Grace M
authors.initials: GM
authors.lastname: Lee
authors.affiliation: Center for Child Health Care Studies, Department of Population Medicine, Harvard Pilgrim Health Care Institute and Harvard Medical School.
authors.forename: Ken
authors.initials: K
authors.lastname: Kleinman
authors.affiliation: Department of Pediatrics, Boston University School of Medicine.
authors.forename: Stephen I
authors.initials: SI
authors.lastname: Pelton
authors.affiliation: Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts.
authors.forename: William
authors.initials: W
authors.lastname: Hanage
authors.affiliation: Division of Infectious Diseases, University of California Irvine.
authors.forename: Susan S
authors.initials: SS
authors.lastname: Huang
authors.affiliation: Center for Child Health Care Studies, Department of Population Medicine, Harvard Pilgrim Health Care Institute and Harvard Medical School.
authors.forename: Matthew
authors.initials: M
authors.lastname: Lakoma
authors.affiliation: Center for Child Health Care Studies, Department of Population Medicine, Harvard Pilgrim Health Care Institute and Harvard Medical School.
authors.forename: Maya
authors.initials: M
authors.lastname: Dutta-Linn
authors.affiliation: Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Croucher
authors.affiliation: Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts.
authors.forename: Abbie
authors.initials: A
authors.lastname: Stevenson
authors.affiliation: Center for Child Health Care Studies, Department of Population Medicine, Harvard Pilgrim Health Care Institute and Harvard Medical School Department of Medicine, Boston Children's Hospital, Massachusetts.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Finkelstein
keywords: Streptococcus pneumoniae; colonization; pneumococcal conjugate vaccine