title: The epidemiology of invasive pneumococcal disease in British Columbia following implementation of an infant immunization program: increases in herd immunity and replacement disease.
abstract: OBJECTIVE
  In 2003, British Columbia (BC) introduced a universal heptavalent pneumococcal conjugate vaccine (PCV-7) program for infants, and in 2007 revised the recommended schedule from four doses to three doses. We describe trends in the incidence of invasive pneumococcal disease (IPD) in association with these program changes.
  
  
  METHODS
  All confirmed cases are reported to the BC Centre for Disease Control (BCCDC) using a standardized data collection process; isolates are forwarded to the BCCDC Public Health and Reference Microbiology Laboratory for serotyping and to the National Reference Laboratory for confirmation. Upon implementation of the reduced dose program in 2007, additional epidemiological data, including immunization history, were collected for children < or = 16 years.
  
  
  RESULTS
  Seven years after implementation of the program, a 78% decline in incidence of IPD among children under five has been achieved; this is largely a direct effect of the PCV-7 program. Among those >16 years of age, herd immunity is evident and decreasing trends of PCV-7 serotypes continued even after the dose reduction program was introduced. However, gains in disease reduction were offset by increases in replacement serotypes, particularly among the over-65 age group. This has resulted in no net change in adult IPD rates.
  
  
  CONCLUSIONS
  The implementation of the PCV-7 program has changed the epidemiology of IPD in BC through direct effects of the vaccine, herd immunity and serotype replacement. The introduction of a three-dose schedule was not associated with an excess of vaccine failures.
authors.affiliation: BC Centre for Disease Control, Epidemiology Services, Vancouver, BC. vanita.sahni@gov.ab.ca
authors.forename: Vanita
authors.initials: V
authors.lastname: Sahni
authors.forename: Monika
authors.initials: M
authors.lastname: Naus
authors.forename: Linda
authors.initials: L
authors.lastname: Hoang
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Tyrrell
authors.forename: Irene
authors.initials: I
authors.lastname: Martin
authors.forename: David M
authors.initials: DM
authors.lastname: Patrick
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016470:Bacteremia / Q000453:epidemiology / Q000382:microbiology / Q000517:prevention & control*; D001955:British Columbia / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D006801:Humans; D032521:Immunity, Herd; D017589:Immunization Programs; D007115:Immunization Schedule; D015994:Incidence; D007223:Infant; D008586:Meningitis, Pneumococcal / Q000453:epidemiology / Q000382:microbiology / Q000517:prevention & control*; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011008:Pneumococcal Infections / Q000453:epidemiology / Q000382:microbiology / Q000517:prevention & control*; D022242:Pneumococcal Vaccines; D011159:Population Surveillance; D013296:Streptococcus pneumoniae / Q000145:classification
chemical_list: D022242:Pneumococcal Vaccines