title: Simultaneous vaccination with MMR and DTaP-IPV-Hib and rate of hospital admissions with any infections: A nationwide register based cohort study.
abstract: In Denmark, live measles, mumps, and rubella vaccine (MMR) is associated with a reduced risk of infectious disease admissions, particularly for lower respiratory tract infections. In low-income countries, simultaneous vaccination (i.e. vaccination at the same visit) with live and inactivated vaccines may increase child mortality compared with the live vaccine alone. We examined the hypothesis that simultaneous administration of MMR and the inactivated DTaP-IPV-Hib vaccine compared with MMR alone is associated with higher incidence of infectious disease admissions.
  
  
  
  Nationwide, retrospective, register based cohort study of 520,859 children born in Denmark 1997-2006, who were followed from 15months to 4years of age. Incidence rate ratios (IRRs) of hospital admissions were estimated by Cox regression and adjusted for background factors including exact age.
  
  
  
  By 2years of age, 4965 children had simultaneous MMR and DTaP-IPV-Hib as their most recent vaccination. Compared with MMR alone, simultaneous administration was associated with a higher rate of lower respiratory tract infections (adjusted incidence rate ratio (IRR), 1.27; 95% confidence interval (CI), 1.13-1.42). There was no effect on other infections. Overall, simultaneous administration was associated with a 7% (95% CI, 0-15%) increase in infectious disease admissions.
  
  
  
  Simultaneous administration of MMR and DTaP-IPV-Hib compared with MMR alone may increase the rate of hospital admissions related to lower respiratory tract infections. These findings require replication in other high-income settings.
authors.affiliation: Research Center for Vitamins and Vaccines (CVIVA), Bandim Health Project, Statens Serum Institut, Copenhagen, Denmark. Electronic address: sgs@ssi.dk.
authors.forename: Signe
authors.initials: S
authors.lastname: Sørup
authors.affiliation: Research Center for Vitamins and Vaccines (CVIVA), Bandim Health Project, Statens Serum Institut, Copenhagen, Denmark; OPEN, Odense Patient Data Explorative Network, Odense University Hospital/Department of Clinical Research, University of Southern Denmark, Odense, Denmark.
authors.forename: Christine S
authors.initials: CS
authors.lastname: Benn
authors.affiliation: Department of Paediatrics and Adolescent Medicine, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Anja
authors.initials: A
authors.lastname: Poulsen
authors.affiliation: Department of Infectious Disease Epidemiology, Statens Serum Institut, Copenhagen, Denmark.
authors.forename: Tyra G
authors.initials: TG
authors.lastname: Krause
authors.affiliation: Research Center for Vitamins and Vaccines (CVIVA), Bandim Health Project, Statens Serum Institut, Copenhagen, Denmark; Bandim Health Project, Indepth Network, Bissau, Guinea-Bissau.
authors.forename: Peter
authors.initials: P
authors.lastname: Aaby
authors.affiliation: Research Center for Vitamins and Vaccines (CVIVA), Bandim Health Project, Statens Serum Institut, Copenhagen, Denmark; OPEN, Odense Patient Data Explorative Network, Odense University Hospital/Department of Clinical Research, University of Southern Denmark, Odense, Denmark.
authors.forename: Henrik
authors.initials: H
authors.lastname: Ravn
mesh_terms: D002675:Child, Preschool; D003718:Denmark / Q000453:epidemiology; D015721:Diphtheria-Tetanus-Pertussis Vaccine / Q000008:administration & dosage / Q000276:immunology*; D005260:Female; D018073:Haemophilus Vaccines / Q000008:administration & dosage / Q000276:immunology*; D006760:Hospitalization; D006801:Humans; D007115:Immunization Schedule; D015994:Incidence; D007223:Infant; D008297:Male; D022542:Measles-Mumps-Rubella Vaccine / Q000008:administration & dosage / Q000276:immunology*; D011054:Poliovirus Vaccine, Inactivated / Q000008:administration & dosage / Q000276:immunology*; D012141:Respiratory Tract Infections / Q000453:epidemiology*; D012189:Retrospective Studies; D017778:Vaccines, Combined / Q000008:administration & dosage / Q000276:immunology
chemical_list: C513012:DTP-IPV-Hib vaccine; D015721:Diphtheria-Tetanus-Pertussis Vaccine; D018073:Haemophilus Vaccines; D022542:Measles-Mumps-Rubella Vaccine; D011054:Poliovirus Vaccine, Inactivated; D017778:Vaccines, Combined
keywords: Heterologous immunity; Infectious disease admissions; Non-targeted effects; Nonspecific effects; Simultaneous immunization