title: Increased risk of hospitalization for acute lower respiratory tract infection among Australian indigenous infants 5-23 months of age following pneumococcal vaccination: a cohort study.
abstract: BACKGROUND
  Australian Indigenous children are the only population worldwide to receive the 7-valent pneumococcal conjugate vaccine (7vPCV) at 2, 4, and 6 months of age and the 23-valent pneumococcal polysaccharide vaccine (23vPPV) at 18 months of age. We evaluated this program's effectiveness in reducing the risk of hospitalization for acute lower respiratory tract infection (ALRI) in Northern Territory (NT) Indigenous children aged 5-23 months.
  
  
  METHODS
  We conducted a retrospective cohort study involving all NT Indigenous children born from 1 April 2000 through 31 October 2004. Person-time at-risk after 0, 1, 2, and 3 doses of 7vPCV and after 0 and 1 dose of 23vPPV and the number of ALRI following each dose were used to calculate dose-specific rates of ALRI for children 5-23 months of age. Rates were compared using Cox proportional hazards models, with the number of doses of each vaccine serving as time-dependent covariates.
  
  
  RESULTS
  There were 5482 children and 8315 child-years at risk, with 2174 episodes of ALRI requiring hospitalization (overall incidence, 261 episodes per 1000 child-years at risk). Elevated risk of ALRI requiring hospitalization was observed after each dose of the 7vPCV vaccine, compared with that for children who received no doses, and an even greater elevation in risk was observed after each dose of the 23vPPV (adjusted hazard ratio [HR] vs no dose, 1.39; 95% confidence interval [CI], 1.12-1.71; P=.002). Risk was highest among children vaccinated with the 23vPPV who had received <3 doses of the 7vPCV (adjusted HR, 1.81; 95% CI, 1.32-2.48).
  
  
  CONCLUSIONS
  Our results suggest an increased risk of ALRI requiring hospitalization after pneumococcal vaccination, particularly after receipt of the 23vPPV booster. The use of the 23vPPV booster should be reevaluated.
authors.affiliation: Child Health Division, Menzies School of Health Research, Charles Darwin University, Tiwi, London, England. kogrady10@gmail.com
authors.forename: Kerry-Ann F
authors.initials: KA
authors.lastname: O'Grady
authors.forename: Katherine J
authors.initials: KJ
authors.lastname: Lee
authors.forename: John B
authors.initials: JB
authors.lastname: Carlin
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Torzillo
authors.forename: Anne B
authors.initials: AB
authors.lastname: Chang
authors.forename: E Kim
authors.initials: EK
authors.lastname: Mulholland
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Lambert
authors.forename: Ross M
authors.initials: RM
authors.lastname: Andrews
mesh_terms: D000208:Acute Disease; D001315:Australia / Q000453:epidemiology; D015331:Cohort Studies; D005260:Female; D005759:Gastroenteritis / Q000453:epidemiology / Q000208:ethnology; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D007223:Infant; D008297:Male; D022242:Pneumococcal Vaccines / Q000008:administration & dosage / Q000009:adverse effects*; D044382:Population Groups; D016016:Proportional Hazards Models; D012141:Respiratory Tract Infections / Q000453:epidemiology* / Q000208:ethnology; D012189:Retrospective Studies; D012307:Risk Factors
chemical_list: C414006:23-valent pneumococcal capsular polysaccharide vaccine; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D022242:Pneumococcal Vaccines