The overall objective of the project is to identify the determinants of antibody-mediated immunity in infants born to mothers immunized during pregnancy. Using maternal pertussis immunization as a model, the project will identify key predictors and potential determinants of vaccine responses in pregnant women, of the transfer of maternal antibodies to the newborn and of vaccine responses in infants. A systems biology approach will be used to delineate pre-vaccination and post-vaccination cellular and molecular correlates of the immune response to pertussis immunization in peripheral blood and in breastmilk.

The overall objective of the project is to identify the determinants of antibody-mediated immunity to pertussis in infants born to mothers immunized during pregnancy. Three specific objectives will be targeted:

1. Determine the impact of pregnancy on the quality of antibody response to pertussis immunization and identify immune predictors of vaccine responses in pregnant and non-pregnant women.
2. Identify immune predictors of the transfer of maternal antibodies to the newborn and the presence of antibody in breastmilk following pertussis immunization during pregnancy.
3. Determine the impact of maternal antibodies on the quality of antibody response to pertussis immunization in infants born to mothers immunized or not immunized during pregnancy and identify immune predictors of vaccine responses in the first months of life.

To reach these objectives, 40 non-pregnant and 80 pregnant women will be recruited into the study and vaccinated with a single dose of a pertussis containing vaccine (Triaxis). Blood samples will be collected from:

• non-pregnant women: before vaccination, and day 1/7/28 and month 5 post-vaccination.
• pregnant women: before vaccination, day 1/7/28 post-vaccination, at delivery, and week 6/12 post-delivery. At week 6/12 post-delivery, breast milk samples will be collected as well.

At delivery, a placenta fragment will be collected.

In addition, infants 2-3 months old born either from mothers who were not vaccinated against pertussis during pregnancy (n=40) or born from mothers who were vaccinated against pertussis during pregnancy (n=80) will be recruited in the study. Infants will be vaccinated with three doses of a pertussis containing vaccine (Vaxelis), each one month apart starting from 2-3 months of age. Blood samples will be collected from:

• infants from vaccinated mothers: cord blood, before 1st vaccine dose, day 1 post 1st vaccine dose, before 3rd vaccine dose, and day 28 post 3rd vaccine dose.
• infants from unvaccinated mothers: before 1st vaccine dose, day 1 post 1st vaccine dose, before 3rd vaccine dose, and day 28 post 3rd vaccine dose.

Inclusion Criteria:

• For non-pregnant & pregnant women Age between 18 and 45 years Eligible for Tdap vaccination
• For infants Born to mothers vaccinated or not with Tdap Vaccinated with hexavalent vaccine Age between 2 and 3 months

Exclusion Criteria:

• For pregnant and non-pregnant women

  • Inability to understand the nature and extent of the study and the procedures required
  • Grade III/IV anemia,
  • Acute infection at the time of immunization
  • Chronic infections such as Hepatitis B Virus (HBV), Hepatitis C Virus (HCV) or Human Immunodeficiency Virus (HIV) infection, acute toxoplasmosis
  • Current or recent use of immunosuppressive drugs
  • Active neoplasia
  • Other vaccine(s) administered at the same time as Tdap vaccination (wash out of 4 weeks after others vaccinations and 28 days after Tdap vaccination )

• For pregnant women

  • Risk of premature delivery or intrauterine growth retardation
  • Twin or triplet pregnancies

• For non-pregnant women Last Tdap vaccination < 12 months before

For infants:

• Infants born before 35 weeks of gestation
• Birthweight below 2.5 kg,
• Severe neonatal distress
• Serious congenital abnormalities or congenital infection.

Researchers analyzing the immunological outcomes will be blinded to the groups of the subjects (pregnant vs non pregnant ; infants)