title: Nasopharyngeal carriage of Streptococcus pneumoniae shortly before vaccination with a pneumococcal conjugate vaccine causes serotype-specific hyporesponsiveness in early infancy.
abstract: BACKGROUND
  The antibody response to pneumococcal conjugate vaccines (PCVs) in infants is variable. Factors responsible for this variability have not been fully elucidated. The objective of this study was to investigate whether pneumococcal carriage around the time of the first dose of 7-valent PCV (PCV7) affects serotype-specific immunologic response.
  
  
  METHODS
  Healthy 2-month old infants were randomized to receive 2 (at the ages of 4 and 6 months) or 3 (at the ages of 2, 4, and 6 months) PCV7 doses and a booster dose (at the age of 12 months). Nasopharyngeal or oropharyngeal specimens were obtained for culture shortly before the first PCV7 dose. Serotype-specific immunoglobulin (Ig) G levels were measured at ages 2, 7, and 13 months.
  
  
  RESULTS
  Of 545 children studied, 332 received a booster dose. The most common serotypes carried around the time of the first PCV7 dose were 6B (n = 37), 19F (n = 22), and 23F (n = 14). In carriers before the first dose, the IgG response to the carried serotype after 2 or 3 doses was significantly lower than in noncarriers. In contrast, response to the noncarried serotypes was not affected. Although all children responded to the booster dose, the response to the originally carried serotype was generally lower.
  
  
  CONCLUSIONS
  Serotype-specific hyporesponsiveness to PCV7 after pneumococcal carriage in infants is demonstrated for the first time. This phenomenon was common, lasted for at least several months, and was only partially overcome by the 12-month booster.
  
  
  BACKGROUND
  isrctn.org identifier: ISRCTN28445844.
authors.affiliation: Pediatric Infectious Disease Unit, Soroka University Medical Center and the Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel. rdagan@bgu.ac.il
authors.forename: Ron
authors.initials: R
authors.lastname: Dagan
authors.forename: Noga
authors.initials: N
authors.lastname: Givon-Lavi
authors.forename: David
authors.initials: D
authors.lastname: Greenberg
authors.forename: Bernard
authors.initials: B
authors.lastname: Fritzell
authors.forename: Claire-Anne
authors.initials: CA
authors.lastname: Siegrist
mesh_terms: D002353:Carrier State; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009305:Nasopharynx / Q000382:microbiology*; D011008:Pneumococcal Infections / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control*; D022242:Pneumococcal Vaccines / Q000008:administration & dosage / Q000276:immunology*; D013296:Streptococcus pneumoniae / Q000302:isolation & purification*
chemical_list: D022242:Pneumococcal Vaccines