title: The effect of underlying clinical conditions on the risk of developing invasive pneumococcal disease in England.
abstract: OBJECTIVE
  To inform national policy making on the use of the 13-valent pneumococcal vaccine among risk groups we estimated the increased risk of invasive pneumococcal disease (IPD) outcomes among clinical risk groups. Three years of post 7-valent pneumococcal conjugate vaccine (PCV7) data was included to investigate the herd protection effects.
  
  
  METHODS
  Over 22,000 IPD patients in England (March 2002-March 2009 - aged 2 and over) were linked to their hospitalisation records. The prevalence of risk factors in these patients was compared to the prevalence of risk factors in the general population.
  
  
  RESULTS
  There was an increased odds ratio (OR) for hospitalisation (OR 11.7 2-15 years; 7.6 16-64; 2.7 65+) and death (OR 2.4 2-15 years, 3.9 16-64, 1.2 65+) from IPD among risk group. The most important risk factors that predict IPD are chronic liver disease, immunosuppression, and chronic respiratory diseases. Herd protection effects due to introduction of the 7-valent vaccine were identical in both patient groups as shown by the similar decline in the proportion of IPD caused by PCV7 serotypes in risk and non-risk groups.
  
  
  CONCLUSIONS
  There is a marked increased risk of IPD among those with certain clinical conditions, suggesting potential benefit from a targeted vaccination approach. However, the indirect protection from conjugate vaccination of children suggests PCV vaccination of high-risk groups may not provide substantial additional benefit once herd immunity takes effect.
authors.affiliation: Immunisation, Hepatitis and Blood Safety Department, Health Protection Services, Colindale, Health Protection Agency, 61 Colindale Avenue, London NW9 5EQ, United Kingdom. albertjan.vanhoek@hpa.org.uk
authors.forename: Albert Jan
authors.initials: AJ
authors.lastname: van Hoek
authors.forename: Nick
authors.initials: N
authors.lastname: Andrews
authors.forename: Pauline A
authors.initials: PA
authors.lastname: Waight
authors.forename: Julia
authors.initials: J
authors.lastname: Stowe
authors.forename: Peter
authors.initials: P
authors.lastname: Gates
authors.forename: Robert
authors.initials: R
authors.lastname: George
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Miller
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016470:Bacteremia / Q000453:epidemiology* / Q000382:microbiology / Q000401:mortality / Q000517:prevention & control; D002648:Child; D002675:Child, Preschool; D015897:Comorbidity; D004739:England / Q000453:epidemiology; D005260:Female; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D006801:Humans; D032521:Immunity, Herd; D008297:Male; D008586:Meningitis, Pneumococcal / Q000453:epidemiology* / Q000382:microbiology / Q000401:mortality / Q000517:prevention & control; D008875:Middle Aged; D022242:Pneumococcal Vaccines / Q000008:administration & dosage / Q000276:immunology; D015995:Prevalence; D012307:Risk Factors; D013296:Streptococcus pneumoniae / Q000276:immunology* / Q000472:pathogenicity*; D016019:Survival Analysis; D055815:Young Adult
chemical_list: C538862:13-valent pneumococcal vaccine; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D022242:Pneumococcal Vaccines