title: Effect of pneumococcal conjugate vaccination on serotype-specific carriage and invasive disease in England: a cross-sectional study.
abstract: BACKGROUND
  We investigated the effect of the 7-valent pneumococcal conjugate vaccine (PCV7) programme in England on serotype-specific carriage and invasive disease to help understand its role in serotype replacement and predict the impact of higher valency vaccines.
  
  
  RESULTS
  Nasopharyngeal swabs were taken from children <5 y old and family members (n=400) 2 y after introduction of PCV7 into routine immunization programs. Proportions carrying Streptococcus pneumoniae and serotype distribution among carried isolates were compared with a similar population prior to PCV7 introduction. Serotype-specific case carrier ratios (CCRs) were estimated using national data on invasive disease. In vaccinated children and their contacts vaccine-type (VT) carriage decreased, but was offset by an increase in non-VT carriage, with no significant overall change in carriage prevalence, odds ratio 1.06 (95% confidence interval 0.76-1.49). The lower CCRs of the replacing serotypes resulted in a net reduction in invasive disease in children. The additional serotypes covered by higher valency vaccines had low carriage but high disease prevalence. Serotype 11C emerged as predominant in carriage but caused no invasive disease whereas 8, 12F, and 22F emerged in disease but had very low carriage prevalence.
  
  
  CONCLUSIONS
  Because the additional serotypes included in PCV10/13 have high CCRs but low carriage prevalence, vaccinating against them is likely to significantly reduce invasive disease with less risk of serotype replacement. However, a few serotypes with high CCRs could mitigate the benefits of higher valency vaccines. Assessment of the effect of PCV on carriage as well as invasive disease should be part of enhanced surveillance activities for PCVs. Please see later in the article for the Editors' Summary.
authors.affiliation: Immunisation, Hepatitis and Blood Safety Department, Health Protection Agency, London, United Kingdom.
authors.forename: Stefan
authors.initials: S
authors.lastname: Flasche
authors.forename: Albert Jan
authors.initials: AJ
authors.lastname: Van Hoek
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Sheasby
authors.forename: Pauline
authors.initials: P
authors.lastname: Waight
authors.forename: Nick
authors.initials: N
authors.lastname: Andrews
authors.forename: Carmen
authors.initials: C
authors.lastname: Sheppard
authors.forename: Robert
authors.initials: R
authors.lastname: George
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Miller
mesh_terms: D000293:Adolescent; D000328:Adult; D002353:Carrier State / Q000276:immunology / Q000382:microbiology*; D002648:Child; D002675:Child, Preschool; D003141:Communicable Diseases / Q000453:epidemiology / Q000276:immunology / Q000382:microbiology; D003430:Cross-Sectional Studies; D004739:England / Q000453:epidemiology; D005260:Female; D006801:Humans; D017589:Immunization Programs; D008297:Male; D009305:Nasopharynx / Q000276:immunology / Q000382:microbiology; D016017:Odds Ratio; D011008:Pneumococcal Infections / Q000453:epidemiology / Q000276:immunology* / Q000382:microbiology; D022242:Pneumococcal Vaccines / Q000276:immunology*; D015995:Prevalence; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification* / Q000276:immunology*; D014611:Vaccination / Q000379:methods*; D018074:Vaccines, Conjugate / Q000276:immunology / Q000382:microbiology*; D055815:Young Adult
chemical_list: D022242:Pneumococcal Vaccines; D018074:Vaccines, Conjugate