title: Effects of 7-valent pneumococcal conjugate 1 vaccine on the severity of adult 2 bacteremic pneumococcal pneumonia.
abstract: OBJECTIVE
  The introduction of a 7-valent conjugate pneumococcal vaccine (PCV7) in children largely affected the prevalence of adult pneumococcal pneumonia. In this study we investigated whether the clinical severity of adult bacteremic pneumococcal pneumonia has also altered following the introduction of pediatric PCV7 vaccination.
  
  
  METHODS
  Adults hospitalized with bacteremic pneumococcal pneumonia between 2001 and June 2011 at two Dutch hospitals were included retrospectively. Clinical data on patient characteristics, comorbidities and severity of disease were obtained and pneumococcal serotypes were determined.
  
  
  RESULTS
  Among 343 patients investigated, those infected with PCV7 serotypes had a higher PSI score (p=0.0072) and mortality rate (p=0.0083) compared with the remainder of the cohort. Since the introduction of PCV7 the proportion of pneumococcal pneumonias caused by serotypes 1 and 7F (p-values 0.037 and 0.025) increased, as well as the rate of pleural effusion and empyema (p-values 0.011 and 0.049). Whilst de proportion of adults infected with PCV7 serotypes decreased after the introduction of PCV7 (p=0.015), PSI scores in these patients remained higher (p=0.030), although mortality rates between PCV7 and non PCV7 types equalized. After the introduction of PCV7 a marked shortening in hospital stay was observed only among patients infected with non PCV7 serotypes (p=0.019).
  
  
  CONCLUSIONS
  The introduction of pediatric PCV7 vaccination was accompanied by subtle changes in clinical severity of adult bacteremic pneumococcal pneumonia. Expansion of serotypes covered by pneumococcal vaccination may again influence the clinical presentation of disease.
authors.affiliation: Department of Pediatrics, Radboud university medical center, 6500 HB Nijmegen, The Netherlands.
authors.forename: Amelieke J H
authors.initials: AJ
authors.lastname: Cremers
authors.affiliation: Department of Medical Microbiology and Infectious Diseases, Canisius Wilhelmina Hospital, 6532 SZ Nijmegen, The Netherlands; Department of Medical Microbiology, Radboud university medical center, 6500 HB Nijmegen, The Netherlands.
authors.forename: Jacques F
authors.initials: JF
authors.lastname: Meis
authors.affiliation: Department of Pediatrics, Radboud university medical center, 6500 HB Nijmegen, The Netherlands.
authors.forename: Grietje
authors.initials: G
authors.lastname: Walraven
authors.affiliation: Department of Pediatrics, Radboud university medical center, 6500 HB Nijmegen, The Netherlands.
authors.forename: Christa E van der Gaast-de
authors.initials: CE
authors.lastname: Jongh
authors.affiliation: Department of Pediatrics, Radboud university medical center, 6500 HB Nijmegen, The Netherlands. Electronic address: Gerben.Ferwerda@radboudumc.nl.
authors.forename: Gerben
authors.initials: G
authors.lastname: Ferwerda
authors.affiliation: Department of Pediatrics, Radboud university medical center, 6500 HB Nijmegen, The Netherlands.
authors.forename: Peter W M
authors.initials: PW
authors.lastname: Hermans
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D005260:Female; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D006760:Hospitalization; D006801:Humans; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D022242:Pneumococcal Vaccines / Q000627:therapeutic use*; D011018:Pneumonia, Pneumococcal / Q000453:epidemiology* / Q000401:mortality; D012703:Serotyping; D012720:Severity of Illness Index; D013296:Streptococcus pneumoniae / Q000145:classification; D018074:Vaccines, Conjugate / Q000627:therapeutic use
chemical_list: D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D022242:Pneumococcal Vaccines; D018074:Vaccines, Conjugate
keywords: Bacteremic pneumococcal pneumonia; Pneumococcal serotypes; Pneumococcal vaccination; Severity of disease