title: Safety of inactivated monovalent pandemic (H1N1) 2009 vaccination during pregnancy: a population-based study in Taiwan.
abstract: BACKGROUND
  Pregnant women were prioritized for H1N1 vaccination during the 2009-2010 pandemic. Safety concerns exist with vaccinating pregnant women, particularly in their first trimesters.
  
  
  METHODS
  We linked computerized data on H1N1 vaccination, National Health Insurance, and Taiwan Birth Registry and identified events of spontaneous abortions (SABs) and all singleton births that occurred/delivered during November 1, 2009-September 30, 2010. The observation period for each case of SAB (6-19 weeks gestation) was divided into period at risk (1-28 days after vaccination) and control periods (the remaining person-days until SAB). The self-controlled case series method for truncated observational periods assessed the incidence rate ratio (IRR) of SAB during the 1-28 days compared with those in the control period. The case-control design matched each case of adverse fetal outcomes to up to 10 controls on fetal sex and year/month of pregnancy onset, and calculated matched odds ratio (OR) on H1N1 vaccination at <14 or ≥14 weeks gestation.
  
  
  RESULTS
  Sixty-five women with SAB had received H1N1 vaccination at 6-19 weeks gestation. The IRR of SAB for the risk period 1-28 days was 1.03 (95% confidence interval [CI] 0.55-1.93). Among the 147,294 live births and 1354 stillbirths, maternal H1N1 vaccine receipt at <14 weeks gestation was associated with significantly reduced likelihood of small for gestational age (SGA) birth (OR 0.72, 95% CI 0.61-0.84) and birth defect (OR 0.46, 95% CI 0.22-1.00), whereas receipt at ≥14 weeks gestation was associated with significantly reduced likelihood of stillbirth (OR 0.63, 95% CI 0.46-0.86), prematurity (OR 0.90, 95% CI 0.83-0.97), low birth weight (OR 0.81, 95% CI 0.74-0.88), and SGA birth (OR 0.90, 95% CI 0.84-0.97).
  
  
  CONCLUSIONS
  H1N1 vaccination during pregnancy did not increase risk of SAB or adverse fetal outcomes.
authors.affiliation: Taiwan Centers for Disease Control, 6 Linsen S. Road, Taipei 10050, Taiwan. Electronic address: huangwt@ntu.edu.tw.
authors.forename: Wan-Ting
authors.initials: WT
authors.lastname: Huang
authors.affiliation: Taiwan Centers for Disease Control, 6 Linsen S. Road, Taipei 10050, Taiwan. Electronic address: pluto0507@hotmail.com.
authors.forename: Fa-Wei
authors.initials: FW
authors.lastname: Tang
authors.affiliation: Taiwan Centers for Disease Control, 6 Linsen S. Road, Taipei 10050, Taiwan. Electronic address: shuer@cdc.gov.tw.
authors.forename: Shu-Er
authors.initials: SE
authors.lastname: Yang
authors.affiliation: Taiwan Centers for Disease Control, 6 Linsen S. Road, Taipei 10050, Taiwan. Electronic address: chih@cdc.gov.tw.
authors.forename: Yi-Chien
authors.initials: YC
authors.lastname: Chih
authors.affiliation: Taiwan Centers for Disease Control, 6 Linsen S. Road, Taipei 10050, Taiwan; Institute of Biomedical Informatics & Institute of Public Health, National Yang-Ming University, 155 Section 2, Linong Street, Taipei 11221, Taiwan. Electronic address: jhchuang@cdc.gov.tw.
authors.forename: Jen-Hsiang
authors.initials: JH
authors.lastname: Chuang
mesh_terms: D000022:Abortion, Spontaneous / Q000453:epidemiology; D000276:Adjuvants, Immunologic / Q000008:administration & dosage; D000328:Adult; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D007252:Influenza Vaccines / Q000009:adverse effects / Q000627:therapeutic use*; D007251:Influenza, Human / Q000517:prevention & control*; D008297:Male; D016017:Odds Ratio; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000517:prevention & control*; D011256:Pregnancy Outcome; D047928:Premature Birth / Q000453:epidemiology; D013624:Taiwan / Q000453:epidemiology; D055815:Young Adult
chemical_list: D000276:Adjuvants, Immunologic; D007252:Influenza Vaccines
keywords: H1N1 virus; MF59 adjuvant; Pregnancy; Taiwan; Vaccine safety