title: Vaccination, underlying comorbidities, and risk of invasive pneumococcal disease.
abstract: OBJECTIVE
  Children with underlying conditions remain at increased risk for invasive pneumococcal diseases (IPD). This study describes the epidemiology, serotype distribution, clinical presentations, and outcomes of IPD in children with and without comorbidity.
  
  
  METHODS
  Cases of childhood IPD in Massachusetts were identified via enhanced surveillance from 2002 through 2014. Demographic and clinical data were collected via follow-up telephone interviews with parents and/or primary care providers. Underlying conditions were classified according to the 2012 Report of the Committee on Infectious Diseases and 2013 recommendations by the Advisory Committee on Immunization Practices.
  
  
  RESULTS
  Among 1052 IPD cases in Massachusetts children <18 years old, 22.1% had at least 1 comorbidity. Immunocompromising conditions (32.7%) and chronic respiratory diseases (22.4%) were most common. Children with comorbidities were older at the time of IPD diagnosis (median 54 vs 23 months, P < .001), had higher hospitalization (odds ratio 2.5; 95% confidence interval 1.7-3.6) and case-fatality rates (odds ratio 3.7; 95% confidence interval 1.5-8.9) compared with children without known underlying conditions after adjusting for age, gender, year of diagnosis, and pneumococcal vaccination status. During the last 2 years of the study, IPD among children with comorbidities was caused by non-pneumococcal conjugate vaccine 13 serotypes in 23-valent polysaccharide pneumococcal vaccine (6/12, 50%) or serotypes that are not included in any of the vaccines (6/12; 50%).
  
  
  CONCLUSIONS
  In children with comorbidity, IPD results in higher mortality, and a large proportion of disease is due to serotypes not included in current conjugate vaccines. Further research is needed, specifically to develop and evaluate additional strategies for prevention of IPD in the most vulnerable children.
authors: Section of Pediatric Infectious Diseases, Boston University Medical Center, Boston, Massachusetts; and Department of Epidemiology, Boston University, School of Public Health, Boston, Massachusetts yildirim@bu.edu.
authors: Inci
authors: I
authors: Yildirim
authors: Section of Pediatric Infectious Diseases, Boston University Medical Center, Boston, Massachusetts; and Department of Epidemiology, Boston University, School of Public Health, Boston, Massachusetts.
authors: Kimberly M
authors: KM
authors: Shea
authors: Section of Pediatric Infectious Diseases, Boston University Medical Center, Boston, Massachusetts; and.
authors: Brent A
authors: BA
authors: Little
authors: Section of Pediatric Infectious Diseases, Boston University Medical Center, Boston, Massachusetts; and.
authors: Amy L
authors: AL
authors: Silverio
authors: Section of Pediatric Infectious Diseases, Boston University Medical Center, Boston, Massachusetts; and Department of Epidemiology, Boston University, School of Public Health, Boston, Massachusetts.
authors: Stephen I
authors: SI
authors: Pelton
mesh_terms: D016667:Bacterial Capsules; D002648:Child; D002675:Child, Preschool; D015897:Comorbidity; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D008404:Massachusetts / Q000453:epidemiology; D011008:Pneumococcal Infections / Q000453:epidemiology* / Q000517:prevention & control; D022242:Pneumococcal Vaccines / Q000494:pharmacology*; D011159:Population Surveillance; D011379:Prognosis; D012189:Retrospective Studies; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D013296:Streptococcus pneumoniae / Q000276:immunology*; D014611:Vaccination / Q000379:methods*; D018074:Vaccines, Conjugate
chemical_list: C414006:23-valent pneumococcal capsular polysaccharide vaccine; D022242:Pneumococcal Vaccines; D018074:Vaccines, Conjugate
keywords: Invasive pneumococcal disease; comorbidity; conjugate vaccines; serotype