title: Timeliness of routine immunization in a population-based Italian cohort of very preterm infants: results of the ACTION follow-up project.
abstract: BACKGROUND
  Although very preterm infants are recommended to receive immunizations, according to their chronological age, immunization start in these infants is often delayed. Aim To measure coverage and timeliness of routine immunizations in Italian very preterm infants and to assess determinants of delay.
  
  
  METHODS
  We followed up infants 22-31 completed weeks of gestational age discharged from intensive care. We measured the proportion of children with one dose of diphtheria-tetanus-pertussis-poliohepatitis, B-Hib vaccine (DTP-Pol-HBV-Hib), measles-mumps-rubella vaccine (MMR), conjugate pneumococcal vaccine (Pnc), conjugate meningococcal C vaccine (MenC), and varicella vaccine (Var) by 24 months. We used the Kaplan Meier method and Cox proportional hazard models to estimate the age, at immunization start and determinants of timeliness for each vaccine.
  
  
  RESULTS
  Data on 1102 (92.1%) children out of 1196 included in the cohort were analyzed. Immunization start by 24 months of age occurred in 95.9% of children for DTP-Pol-HBV-Hib; 84.0% for MMR; 49.7% for Pnc; 38.5% for MenC; and 4.1% for Var. Eighty-seven percent of participants received the first dose of DTP-Pol-HBV-Hib by 6 months of age, and 66.7% had their first MMR administered by 18 months. Hospitalization was associated with delay for all vaccines with the exception of MenC and Var. Maternal employment was associated with earlier immunization for MMR, Pnc, and MenC. DTP-Pol-HBV-Hib timeliness improved with increasing birthweight and paternal employment and decreased with a larger number of siblings in the household. MMR was delayed in children with cerebral palsy, and in those with a larger number of children in the household. Immunization for Pnc was delayed in children with larger number of siblings.
  
  
  CONCLUSIONS
  Immunization start for all vaccines was considerably delayed in many very preterm infants. Public health strategies taking into account determinants of delay should be implemented to improve coverage and timeliness of vaccination in this group of infants.
authors.affiliation: Unit of Epidemiology, Bambino Gesù Children's Hospital IRCCS, Rome, Italy. Electronic address: albertoeugenio.tozzi@opbg.net.
authors.forename: Alberto E
authors.initials: AE
authors.lastname: Tozzi
authors.affiliation: Unit of Epidemiology, Bambino Gesù Children's Hospital IRCCS, Rome, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Piga
authors.affiliation: International Centre on Birth Defects and Prematurity, Rome, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Corchia
authors.affiliation: Regional Health Agency of Lazio, Rome, Italy.
authors.forename: Domenico
authors.initials: D
authors.lastname: Di Lallo
authors.affiliation: Maternal and Child Health Institute, Marche University and Salesi Hospital, Ancona, Italy.
authors.forename: Virgilio
authors.initials: V
authors.lastname: Carnielli
authors.affiliation: Neonatal Intensive Care Unit, S. Maria della Misericordia University Hospital, Udine, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Chiandotto
authors.affiliation: Neonatal Intensive Care Unit, Burlo Garofolo Maternal and Child Health Institute, IRCCS, Trieste, Italy.
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Fertz
authors.affiliation: Neonatal Intensive Care Unit, Pugliese-Ciaccio Hospital, Catanzaro, Italy.
authors.forename: Silvana
authors.initials: S
authors.lastname: Miniaci
authors.affiliation: Unit of Epidemiology, Anna Meyer Children's University Hospital and Regional Agency for Health of Tuscany, Florence, Italy.
authors.forename: Franca
authors.initials: F
authors.lastname: Rusconi
authors.affiliation: Unit of Epidemiology, Bambino Gesù Children's Hospital IRCCS, Rome, Italy.
authors.forename: Marina
authors.initials: M
authors.lastname: Cuttini
mesh_terms: D019433:Chickenpox Vaccine / Q000008:administration & dosage; D015721:Diphtheria-Tetanus-Pertussis Vaccine / Q000008:administration & dosage; D005260:Female; D005500:Follow-Up Studies; D019983:Guideline Adherence; D018073:Haemophilus Vaccines / Q000008:administration & dosage; D017325:Hepatitis B Vaccines / Q000008:administration & dosage; D006801:Humans; D007115:Immunization Schedule; D007223:Infant; D007234:Infant, Premature; D007558:Italy; D053208:Kaplan-Meier Estimate; D008297:Male; D022542:Measles-Mumps-Rubella Vaccine / Q000008:administration & dosage; D022401:Meningococcal Vaccines / Q000008:administration & dosage; D022242:Pneumococcal Vaccines / Q000008:administration & dosage; D011054:Poliovirus Vaccine, Inactivated / Q000008:administration & dosage; D016016:Proportional Hazards Models; D013997:Time Factors; D014611:Vaccination / Q000706:statistics & numerical data*; D017778:Vaccines, Combined / Q000008:administration & dosage
chemical_list: D019433:Chickenpox Vaccine; D015721:Diphtheria-Tetanus-Pertussis Vaccine; D018073:Haemophilus Vaccines; D017325:Hepatitis B Vaccines; D022542:Measles-Mumps-Rubella Vaccine; D022401:Meningococcal Vaccines; D022242:Pneumococcal Vaccines; D011054:Poliovirus Vaccine, Inactivated; D017778:Vaccines, Combined; C541235:diphtheria-tetanus-acellular pertussis-inactivated poliovirus-Haemophilus influenzae b conjugate-hepatitis B vaccine; C410218:serogroup C meningococcal conjugate vaccine
keywords: Immunization; Immunization age; Immunization rate; Preterm infants