title: Infant Respiratory Outcomes Associated with Prenatal Exposure to Maternal 2009 A/H1N1 Influenza Vaccination.
abstract: BACKGROUND
  Infants are at high risk for influenza illness, but are ineligible for vaccination before 6 months. Transfer of maternal antibodies to the fetus has been demonstrated for 2009 A/H1N1 pandemic vaccines; however, clinical effectiveness is unknown. Our objective was to evaluate the association between 2009 A/H1N1 pandemic vaccination during pregnancy and rates of infant influenza and pneumonia.
  
  
  METHODS
  We linked a population-based birth cohort to administrative databases to measure rates of influenza and pneumonia diagnosed during ambulatory physician visits, hospitalizations and emergency department visits during one year of follow-up. We estimated incidence rate ratios and 95% confidence intervals (95% CI) using Poisson regression, comparing infants born to A/H1N1-vaccinated women (vaccine-exposed infants) with unexposed infants, adjusted for confounding using high-dimensional propensity scores.
  
  
  RESULTS
  Among 117,335 infants in the study, 36,033 (31%) were born to A/H1N1-vaccinated women. Crude rates of influenza during the pandemic (per 100,000 infant-days) for vaccine-exposed and unexposed infants were similar (2.19, 95% CI: 1.27-3.76 and 3.60, 95% CI: 2.51-5.14, respectively), as were crude rates of influenza and pneumonia combined. We did not observe any significant differences in rates of study outcomes between study groups during the second wave of the 2009 A/H1N1 pandemic, nor during any post-pandemic time period.
  
  
  CONCLUSIONS
  We observed no difference in rates of study outcomes among infants born to A/H1N1-vaccinated mothers relative to unexposed infants born during the second A/H1N1 pandemic wave; however, due to late availability of the pandemic vaccine, the available follow-up time during the pandemic time period was very limited.
authors.affiliation: Better Outcomes Registry & Network (BORN) Ontario, Ottawa, Ontario, Canada.
authors.forename: Deshayne B
authors.initials: DB
authors.lastname: Fell
authors.affiliation: Department of Medicine, University of Ottawa, Ottawa, Ontario, Canada.|Institute for Clinical Evaluative Sciences, Ottawa and Toronto, Ontario, Canada.|Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada.
authors.forename: Kumanan
authors.initials: K
authors.lastname: Wilson
authors.affiliation: Institute for Clinical Evaluative Sciences, Ottawa and Toronto, Ontario, Canada.|Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada.
authors.forename: Robin
authors.initials: R
authors.lastname: Ducharme
authors.affiliation: Institute for Clinical Evaluative Sciences, Ottawa and Toronto, Ontario, Canada.|Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada.|School of Epidemiology, Public Health and Preventive Medicine, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Steven
authors.initials: S
authors.lastname: Hawken
authors.affiliation: Better Outcomes Registry & Network (BORN) Ontario, Ottawa, Ontario, Canada.
authors.forename: Ann E
authors.initials: AE
authors.lastname: Sprague
authors.affiliation: Institute for Clinical Evaluative Sciences, Ottawa and Toronto, Ontario, Canada.|Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.|Public Health Ontario, Toronto, Ontario, Canada.|Department of Family and Community Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Kwong
authors.affiliation: Department of Obstetrics & Gynaecology, Queen's University, Kingston, Ontario, Canada.
authors.forename: Graeme
authors.initials: G
authors.lastname: Smith
authors.affiliation: Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada.|OMNI Research Group, Department of Obstetrics and Gynecology, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Shi Wu
authors.initials: SW
authors.lastname: Wen
authors.affiliation: Better Outcomes Registry & Network (BORN) Ontario, Ottawa, Ontario, Canada.|Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada.|OMNI Research Group, Department of Obstetrics and Gynecology, University of Ottawa, Ottawa, Ontario, Canada.|Department of Obstetrics, Gynecology and Newborn Care, The Ottawa Hospital, Ottawa, Ontario, Canada.
authors.forename: Mark C
authors.initials: MC
authors.lastname: Walker
mesh_terms: D000328:Adult; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007232:Infant, Newborn, Diseases / Q000453:epidemiology / Q000209:etiology; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000009:adverse effects / Q000627:therapeutic use*; D007251:Influenza, Human / Q000151:congenital / Q000453:epidemiology* / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D011014:Pneumonia / Q000151:congenital / Q000453:epidemiology* / Q000209:etiology; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000453:epidemiology* / Q000209:etiology / Q000276:immunology; D012127:Respiratory Distress Syndrome, Newborn / Q000453:epidemiology / Q000209:etiology; D012189:Retrospective Studies; D016896:Treatment Outcome; D014611:Vaccination / Q000009:adverse effects* / Q000706:statistics & numerical data; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines