title: Pneumococcal-specific IgG levels after 13-valent pneumococcal conjugate vaccination in Nigerian children with sickle cell disease.
abstract: BACKGROUND
  Children with sickle cell disease (SCD) are particularly susceptible to pneumococcal infection. Administration of the 13-valent conjugate pneumococcal vaccine which is now available in Nigeria may help to reduce the incidence.
  
  
  OBJECTIVE
  To determine the serum level of pneumococcal-specific IgG (PIgG) in a cohort of patients with SCD after administration of a single-dose of a 13-valent pneumococcal conjugate vaccine.
  
  
  METHODS
  The study was conducted between December 2011 and March 2012 among children with SCD aged 5 months to 5 years attending the sickle cell clinic in five public hospitals in Lagos. Altogether, 151 children with SCD and 52 without it (controls) were recruited by convenience sampling from the sickle cell clinics and well-child clinics. Blood samples were collected for PIgG concentrations before and 2 months after a single dose of the Prevenar 13 vaccine. Seroconversion was defined as a fourfold or greater increase in antibody concentration after vaccination while those with PIgG concentrations ≥200 μU/ml were considered to have protective levels.
  
  
  RESULTS
  The age range of the total study group was 5-60 months with a mean (SD) of 39.04 (15.44) months and a median of 39 months. The mean (SD) ages of subjects with and without SCD were 38.91 (15.75) months and 16.39 (15.45) months, respectively. The PIgG concentration 2 months post-vaccination was significantly greater than the pre-vaccination levels in all age categories in both groups and almost all subjects had protective PIgG concentrations 2 months after vaccination. A four-fold increase in PIgG concentration was detected more commonly in the controls than in SCD patients.
  
  
  CONCLUSIONS
  Prevenar 13 provided protective immunity in all vaccinated children but those under 2 years of age who had non-protective levels pre-vaccination benefited the most.
authors.affiliation: a Department of Paediatrics , Lagos State University Teaching Hospital.
authors.forename: E A
authors.initials: EA
authors.lastname: Disu
authors.affiliation: a Department of Paediatrics , Lagos State University Teaching Hospital.
authors.forename: S O
authors.initials: SO
authors.lastname: Akodu
authors.affiliation: b Immunology Unit, Department of Chemical Pathology.
authors.forename: O G
authors.initials: OG
authors.lastname: Arinola
authors.affiliation: a Department of Paediatrics , Lagos State University Teaching Hospital.
authors.forename: I N
authors.initials: IN
authors.lastname: Diaku-Akinwumi
authors.affiliation: c Department of Epidemiology and Medical Statistics, College of Medicine , University of Ibadan , Nigeria.
authors.forename: B
authors.initials: B
authors.lastname: Adedokun
authors.affiliation: d Section of Pulmonary and Critical Care Medicine, Center for Global Health , University of Chicago , USA.
authors.forename: C O
authors.initials: CO
authors.lastname: Olopade
authors.affiliation: a Department of Paediatrics , Lagos State University Teaching Hospital.
authors.forename: O F
authors.initials: OF
authors.lastname: Njokanma
mesh_terms: D000755:Anemia, Sickle Cell / Q000276:immunology*; D000907:Antibodies, Bacterial / Q000097:blood*; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007223:Infant; D008297:Male; D009549:Nigeria; D022242:Pneumococcal Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D011446:Prospective Studies
chemical_list: C538862:13-valent pneumococcal vaccine; D000907:Antibodies, Bacterial; D007074:Immunoglobulin G; D022242:Pneumococcal Vaccines
keywords: Antibody; Conjugate vaccine; IgG; Immunisation; Nigeria; Pneumococcal; Seroconversion; Sickle cell disease