title: PCV7-induced changes in pneumococcal carriage and invasive disease burden in Alaskan children.
abstract: BACKGROUND
  Changes in pneumococcal serotype-specific carriage and invasive pneumococcal disease (IPD) after the introduction of pneumococcal conjugate vaccine (PCV7) could inform serotype epidemiology patterns following the introduction of newer conjugate vaccines.
  
  
  METHODS
  We used data from statewide IPD surveillance and annual pneumococcal carriage studies in four regions of Alaska to calculate serotype-specific invasiveness ratios (IR; odds ratio of a carried serotype's likelihood to cause invasive disease compared to other serotypes) in children <5 years of age. We describe changes in carriage, disease burden, and invasiveness between two time periods, the pre-PCV7 period (1996-2000) and the late post-PCV7 period (2006-2009).
  
  
  RESULTS
  Incidence of IPD decreased from the pre- to post-vaccine period (95.7 vs. 57.2 cases per 100,000 children, P<0.001), with a 99% reduction in PCV7 disease. Carriage prevalence did not change between the two periods (49% vs. 50%), although PCV7 serotype carriage declined by 97%, and non-vaccine serotypes increased in prevalence. Alaska pre-vaccine IRs corresponded to pooled results from eight pre-vaccine comparator studies (Spearman's rho=0.44, P=0.002) and to the Alaska post-vaccine period (Spearman's rho=0.28, P=0.029). Relatively invasive serotypes (IR>1) caused 66% of IPD in both periods, although fewer serotypes with IR>1 remained in the post-vaccine (n=9) than the pre-vaccine period (n=13).
  
  
  CONCLUSIONS
  After PCV7 introduction, serotype IRs changed little, and four of the most invasive serotypes were nearly eliminated. If PCV13 use leads to a reduction of carriage and IPD for the 13 vaccine serotypes, the overall IPD rate should further decline.
  The findings and conclusions in this report are those of the author(s) and do not necessarily represent the official position of the Centers for Disease Control and Prevention.
authors.affiliation: Epidemic Intelligence Service, Centers for Disease Control and Prevention, 600 Clifton Rd Atlanta, GA 30333, USA; Arctic Investigations Program, Centers for Disease Control and Prevention, 4055 Tudor Centre Dr., Anchorage, AK 99508, USA. Electronic address: jameswkeck@gmail.com.
authors.forename: James W
authors.initials: JW
authors.lastname: Keck
authors.affiliation: Arctic Investigations Program, Centers for Disease Control and Prevention, 4055 Tudor Centre Dr., Anchorage, AK 99508, USA.
authors.forename: Jay D
authors.initials: JD
authors.lastname: Wenger
authors.affiliation: Arctic Investigations Program, Centers for Disease Control and Prevention, 4055 Tudor Centre Dr., Anchorage, AK 99508, USA.
authors.forename: Dana L
authors.initials: DL
authors.lastname: Bruden
authors.affiliation: Arctic Investigations Program, Centers for Disease Control and Prevention, 4055 Tudor Centre Dr., Anchorage, AK 99508, USA.
authors.forename: Karen M
authors.initials: KM
authors.lastname: Rudolph
authors.affiliation: Arctic Investigations Program, Centers for Disease Control and Prevention, 4055 Tudor Centre Dr., Anchorage, AK 99508, USA.
authors.forename: Debby A
authors.initials: DA
authors.lastname: Hurlburt
authors.affiliation: Arctic Investigations Program, Centers for Disease Control and Prevention, 4055 Tudor Centre Dr., Anchorage, AK 99508, USA.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Hennessy
authors.affiliation: Arctic Investigations Program, Centers for Disease Control and Prevention, 4055 Tudor Centre Dr., Anchorage, AK 99508, USA.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Bruce
mesh_terms: D000413:Alaska / Q000453:epidemiology; D002353:Carrier State / Q000453:epidemiology*; D002675:Child, Preschool; D017281:Cost of Illness; D062665:Epidemiological Monitoring; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D006801:Humans; D015994:Incidence; D011008:Pneumococcal Infections / Q000453:epidemiology* / Q000517:prevention & control; D022242:Pneumococcal Vaccines / Q000008:administration & dosage*; D065288:Serogroup; D013997:Time Factors; D018074:Vaccines, Conjugate / Q000008:administration & dosage
chemical_list: C538862:13-valent pneumococcal vaccine; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D022242:Pneumococcal Vaccines; D018074:Vaccines, Conjugate
keywords: Alaska; Invasiveness; Pneumococcal carriage; Pneumococcal conjugate vaccine; Pneumococcal disease