Influenza vaccination given at least 2 weeks before delivery to pregnant women facilitates transmission of seroprotective influenza-specific antibodies to the newborn

Pediatr Infect Dis J. 2013 Dec;32(12):1374-80. doi: 10.1097/01.inf.0000437066.40840.c4.


Background: Pregnant women and infants are at higher risk of complications secondary to influenza infection. Immunization during pregnancy facilitates protection of the neonates through passive transfer of maternal antibodies.

Methods: This was a cross-sectional study performed during the post-H1N1 pandemic winter season of 2010/2011 in Geneva, Switzerland. We measured antibody titers against the seasonal influenza A H1N1, H3N2 and B 2010/2011 strains by hemagglutination inhibition in the umbilical cord blood of newborns born to vaccinated and nonvaccinated mothers. Seroprotection was defined as a hemagglutination inhibition titer ≥ 40.

Results: A total of 188 women were enrolled, 101 of whom had been vaccinated with a nonadjuvanted influenza vaccine (all during the second or third trimester) and the other 87 had not. Among newborns of vaccinated women, 84-86% showed seroprotective levels depending on the strain. In comparison, seroprotection rates were significantly lower in babies of nonvaccinated women (29-33%, P < 0.001). Adjusting for various confounding factors and applying multivariate regression analysis, vaccination during pregnancy ≥ 2 weeks before delivery increased geometric mean titers in umbilical cord blood 5-17 times and seroprotection rates 5.8-34.4 times, depending on the strain and the interval between vaccination and delivery. Vaccinating pregnant women only 2-4 weeks before delivery was still more effective than no vaccination at all (geometric mean titers increased 6.8-11.1 times and seroprotection rates increased 5.8-34.4 times compared with nonvaccinated women).

Conclusions: Influenza vaccination at any time during the second and third trimester of pregnancy, but at least 15 days before delivery, confers seroprotection to many neonates.

MeSH terms

  • Adult
  • Antibodies, Viral / blood*
  • Antigens, Viral / immunology
  • Cross-Sectional Studies
  • Female
  • Fetal Blood / chemistry
  • Fetal Blood / immunology
  • Hemagglutination Inhibition Tests
  • Humans
  • Immunity, Maternally-Acquired / immunology*
  • Infant, Newborn
  • Influenza A Virus, H1N1 Subtype / immunology
  • Influenza A Virus, H3N2 Subtype / immunology
  • Influenza B virus / immunology
  • Influenza Vaccines / administration & dosage*
  • Influenza Vaccines / immunology*
  • Influenza, Human / immunology
  • Influenza, Human / prevention & control*
  • Pregnancy
  • Pregnancy Complications, Infectious / immunology
  • Pregnancy Complications, Infectious / prevention & control*


  • Antibodies, Viral
  • Antigens, Viral
  • Influenza Vaccines